Merge branch 'maint'

[alt-git.git] / builtin / index-pack.c

#include "builtin.h"
#include "delta.h"
#include "pack.h"
#include "csum-file.h"
#include "blob.h"
#include "commit.h"
#include "tag.h"
#include "tree.h"
#include "progress.h"
#include "fsck.h"
#include "exec_cmd.h"

static const char index_pack_usage[] =
"git index-pack [-v] [-o <index-file>] [--keep | --keep=<msg>] [--verify] [--strict] (<pack-file> | --stdin [--fix-thin] [<pack-file>])";

struct object_entry {
        struct pack_idx_entry idx;
        unsigned long size;
        unsigned int hdr_size;
        enum object_type type;
        enum object_type real_type;
        unsigned delta_depth;
        int base_object_no;
};

union delta_base {
        unsigned char sha1[20];
        off_t offset;
};

struct base_data {
        struct base_data *base;
        struct base_data *child;
        struct object_entry *obj;
        void *data;
        unsigned long size;
        int ref_first, ref_last;
        int ofs_first, ofs_last;
};

/*
 * Even if sizeof(union delta_base) == 24 on 64-bit archs, we really want
 * to memcmp() only the first 20 bytes.
 */
#define UNION_BASE_SZ   20

#define FLAG_LINK (1u<<20)
#define FLAG_CHECKED (1u<<21)

struct delta_entry {
        union delta_base base;
        int obj_no;
};

static struct object_entry *objects;
static struct delta_entry *deltas;
static struct base_data *base_cache;
static size_t base_cache_used;
static int nr_objects;
static int nr_deltas;
static int nr_resolved_deltas;

static int from_stdin;
static int strict;
static int verbose;

static struct progress *progress;

/* We always read in 4kB chunks. */
static unsigned char input_buffer[4096];
static unsigned int input_offset, input_len;
static off_t consumed_bytes;
static unsigned deepest_delta;
static git_SHA_CTX input_ctx;
static uint32_t input_crc32;
static int input_fd, output_fd, pack_fd;

static int mark_link(struct object *obj, int type, void *data)
{
        if (!obj)
                return -1;

        if (type != OBJ_ANY && obj->type != type)
                die("object type mismatch at %s", sha1_to_hex(obj->sha1));

        obj->flags |= FLAG_LINK;
        return 0;
}

/* The content of each linked object must have been checked
   or it must be already present in the object database */
static void check_object(struct object *obj)
{
        if (!obj)
                return;

        if (!(obj->flags & FLAG_LINK))
                return;

        if (!(obj->flags & FLAG_CHECKED)) {
                unsigned long size;
                int type = sha1_object_info(obj->sha1, &size);
                if (type != obj->type || type <= 0)
                        die("object of unexpected type");
                obj->flags |= FLAG_CHECKED;
                return;
        }
}

static void check_objects(void)
{
        unsigned i, max;

        max = get_max_object_index();
        for (i = 0; i < max; i++)
                check_object(get_indexed_object(i));
}


/* Discard current buffer used content. */
static void flush(void)
{
        if (input_offset) {
                if (output_fd >= 0)
                        write_or_die(output_fd, input_buffer, input_offset);
                git_SHA1_Update(&input_ctx, input_buffer, input_offset);
                memmove(input_buffer, input_buffer + input_offset, input_len);
                input_offset = 0;
        }
}

/*
 * Make sure at least "min" bytes are available in the buffer, and
 * return the pointer to the buffer.
 */
static void *fill(int min)
{
        if (min <= input_len)
                return input_buffer + input_offset;
        if (min > sizeof(input_buffer))
                die("cannot fill %d bytes", min);
        flush();
        do {
                ssize_t ret = xread(input_fd, input_buffer + input_len,
                                sizeof(input_buffer) - input_len);
                if (ret <= 0) {
                        if (!ret)
                                die("early EOF");
                        die_errno("read error on input");
                }
                input_len += ret;
                if (from_stdin)
                        display_throughput(progress, consumed_bytes + input_len);
        } while (input_len < min);
        return input_buffer;
}

static void use(int bytes)
{
        if (bytes > input_len)
                die("used more bytes than were available");
        input_crc32 = crc32(input_crc32, input_buffer + input_offset, bytes);
        input_len -= bytes;
        input_offset += bytes;

        /* make sure off_t is sufficiently large not to wrap */
        if (signed_add_overflows(consumed_bytes, bytes))
                die("pack too large for current definition of off_t");
        consumed_bytes += bytes;
}

static const char *open_pack_file(const char *pack_name)
{
        if (from_stdin) {
                input_fd = 0;
                if (!pack_name) {
                        static char tmp_file[PATH_MAX];
                        output_fd = odb_mkstemp(tmp_file, sizeof(tmp_file),
                                                "pack/tmp_pack_XXXXXX");
                        pack_name = xstrdup(tmp_file);
                } else
                        output_fd = open(pack_name, O_CREAT|O_EXCL|O_RDWR, 0600);
                if (output_fd < 0)
                        die_errno("unable to create '%s'", pack_name);
                pack_fd = output_fd;
        } else {
                input_fd = open(pack_name, O_RDONLY);
                if (input_fd < 0)
                        die_errno("cannot open packfile '%s'", pack_name);
                output_fd = -1;
                pack_fd = input_fd;
        }
        git_SHA1_Init(&input_ctx);
        return pack_name;
}

static void parse_pack_header(void)
{
        struct pack_header *hdr = fill(sizeof(struct pack_header));

        /* Header consistency check */
        if (hdr->hdr_signature != htonl(PACK_SIGNATURE))
                die("pack signature mismatch");
        if (!pack_version_ok(hdr->hdr_version))
                die("pack version %"PRIu32" unsupported",
                        ntohl(hdr->hdr_version));

        nr_objects = ntohl(hdr->hdr_entries);
        use(sizeof(struct pack_header));
}

static NORETURN void bad_object(unsigned long offset, const char *format,
                       ...) __attribute__((format (printf, 2, 3)));

static NORETURN void bad_object(unsigned long offset, const char *format, ...)
{
        va_list params;
        char buf[1024];

        va_start(params, format);
        vsnprintf(buf, sizeof(buf), format, params);
        va_end(params);
        die("pack has bad object at offset %lu: %s", offset, buf);
}

static struct base_data *alloc_base_data(void)
{
        struct base_data *base = xmalloc(sizeof(struct base_data));
        memset(base, 0, sizeof(*base));
        base->ref_last = -1;
        base->ofs_last = -1;
        return base;
}

static void free_base_data(struct base_data *c)
{
        if (c->data) {
                free(c->data);
                c->data = NULL;
                base_cache_used -= c->size;
        }
}

static void prune_base_data(struct base_data *retain)
{
        struct base_data *b;
        for (b = base_cache;
             base_cache_used > delta_base_cache_limit && b;
             b = b->child) {
                if (b->data && b != retain)
                        free_base_data(b);
        }
}

static void link_base_data(struct base_data *base, struct base_data *c)
{
        if (base)
                base->child = c;
        else
                base_cache = c;

        c->base = base;
        c->child = NULL;
        if (c->data)
                base_cache_used += c->size;
        prune_base_data(c);
}

static void unlink_base_data(struct base_data *c)
{
        struct base_data *base = c->base;
        if (base)
                base->child = NULL;
        else
                base_cache = NULL;
        free_base_data(c);
}

static void *unpack_entry_data(unsigned long offset, unsigned long size)
{
        int status;
        git_zstream stream;
        void *buf = xmalloc(size);

        memset(&stream, 0, sizeof(stream));
        git_inflate_init(&stream);
        stream.next_out = buf;
        stream.avail_out = size;

        do {
                stream.next_in = fill(1);
                stream.avail_in = input_len;
                status = git_inflate(&stream, 0);
                use(input_len - stream.avail_in);
        } while (status == Z_OK);
        if (stream.total_out != size || status != Z_STREAM_END)
                bad_object(offset, "inflate returned %d", status);
        git_inflate_end(&stream);
        return buf;
}

static void *unpack_raw_entry(struct object_entry *obj, union delta_base *delta_base)
{
        unsigned char *p;
        unsigned long size, c;
        off_t base_offset;
        unsigned shift;
        void *data;

        obj->idx.offset = consumed_bytes;
        input_crc32 = crc32(0, NULL, 0);

        p = fill(1);
        c = *p;
        use(1);
        obj->type = (c >> 4) & 7;
        size = (c & 15);
        shift = 4;
        while (c & 0x80) {
                p = fill(1);
                c = *p;
                use(1);
                size += (c & 0x7f) << shift;
                shift += 7;
        }
        obj->size = size;

        switch (obj->type) {
        case OBJ_REF_DELTA:
                hashcpy(delta_base->sha1, fill(20));
                use(20);
                break;
        case OBJ_OFS_DELTA:
                memset(delta_base, 0, sizeof(*delta_base));
                p = fill(1);
                c = *p;
                use(1);
                base_offset = c & 127;
                while (c & 128) {
                        base_offset += 1;
                        if (!base_offset || MSB(base_offset, 7))
                                bad_object(obj->idx.offset, "offset value overflow for delta base object");
                        p = fill(1);
                        c = *p;
                        use(1);
                        base_offset = (base_offset << 7) + (c & 127);
                }
                delta_base->offset = obj->idx.offset - base_offset;
                if (delta_base->offset <= 0 || delta_base->offset >= obj->idx.offset)
                        bad_object(obj->idx.offset, "delta base offset is out of bound");
                break;
        case OBJ_COMMIT:
        case OBJ_TREE:
        case OBJ_BLOB:
        case OBJ_TAG:
                break;
        default:
                bad_object(obj->idx.offset, "unknown object type %d", obj->type);
        }
        obj->hdr_size = consumed_bytes - obj->idx.offset;

        data = unpack_entry_data(obj->idx.offset, obj->size);
        obj->idx.crc32 = input_crc32;
        return data;
}

static void *get_data_from_pack(struct object_entry *obj)
{
        off_t from = obj[0].idx.offset + obj[0].hdr_size;
        unsigned long len = obj[1].idx.offset - from;
        unsigned char *data, *inbuf;
        git_zstream stream;
        int status;

        data = xmalloc(obj->size);
        inbuf = xmalloc((len < 64*1024) ? len : 64*1024);

        memset(&stream, 0, sizeof(stream));
        git_inflate_init(&stream);
        stream.next_out = data;
        stream.avail_out = obj->size;

        do {
                ssize_t n = (len < 64*1024) ? len : 64*1024;
                n = pread(pack_fd, inbuf, n, from);
                if (n < 0)
                        die_errno("cannot pread pack file");
                if (!n)
                        die("premature end of pack file, %lu bytes missing", len);
                from += n;
                len -= n;
                stream.next_in = inbuf;
                stream.avail_in = n;
                status = git_inflate(&stream, 0);
        } while (len && status == Z_OK && !stream.avail_in);

        /* This has been inflated OK when first encountered, so... */
        if (status != Z_STREAM_END || stream.total_out != obj->size)
                die("serious inflate inconsistency");

        git_inflate_end(&stream);
        free(inbuf);
        return data;
}

static int compare_delta_bases(const union delta_base *base1,
                               const union delta_base *base2,
                               enum object_type type1,
                               enum object_type type2)
{
        int cmp = type1 - type2;
        if (cmp)
                return cmp;
        return memcmp(base1, base2, UNION_BASE_SZ);
}

static int find_delta(const union delta_base *base, enum object_type type)
{
        int first = 0, last = nr_deltas;

        while (first < last) {
                int next = (first + last) / 2;
                struct delta_entry *delta = &deltas[next];
                int cmp;

                cmp = compare_delta_bases(base, &delta->base,
                                          type, objects[delta->obj_no].type);
                if (!cmp)
                        return next;
                if (cmp < 0) {
                        last = next;
                        continue;
                }
                first = next+1;
        }
        return -first-1;
}

static void find_delta_children(const union delta_base *base,
                                int *first_index, int *last_index,
                                enum object_type type)
{
        int first = find_delta(base, type);
        int last = first;
        int end = nr_deltas - 1;

        if (first < 0) {
                *first_index = 0;
                *last_index = -1;
                return;
        }
        while (first > 0 && !memcmp(&deltas[first - 1].base, base, UNION_BASE_SZ))
                --first;
        while (last < end && !memcmp(&deltas[last + 1].base, base, UNION_BASE_SZ))
                ++last;
        *first_index = first;
        *last_index = last;
}

static void sha1_object(const void *data, unsigned long size,
                        enum object_type type, unsigned char *sha1)
{
        hash_sha1_file(data, size, typename(type), sha1);
        if (has_sha1_file(sha1)) {
                void *has_data;
                enum object_type has_type;
                unsigned long has_size;
                has_data = read_sha1_file(sha1, &has_type, &has_size);
                if (!has_data)
                        die("cannot read existing object %s", sha1_to_hex(sha1));
                if (size != has_size || type != has_type ||
                    memcmp(data, has_data, size) != 0)
                        die("SHA1 COLLISION FOUND WITH %s !", sha1_to_hex(sha1));
                free(has_data);
        }
        if (strict) {
                if (type == OBJ_BLOB) {
                        struct blob *blob = lookup_blob(sha1);
                        if (blob)
                                blob->object.flags |= FLAG_CHECKED;
                        else
                                die("invalid blob object %s", sha1_to_hex(sha1));
                } else {
                        struct object *obj;
                        int eaten;
                        void *buf = (void *) data;

                        /*
                         * we do not need to free the memory here, as the
                         * buf is deleted by the caller.
                         */
                        obj = parse_object_buffer(sha1, type, size, buf, &eaten);
                        if (!obj)
                                die("invalid %s", typename(type));
                        if (fsck_object(obj, 1, fsck_error_function))
                                die("Error in object");
                        if (fsck_walk(obj, mark_link, NULL))
                                die("Not all child objects of %s are reachable", sha1_to_hex(obj->sha1));

                        if (obj->type == OBJ_TREE) {
                                struct tree *item = (struct tree *) obj;
                                item->buffer = NULL;
                        }
                        if (obj->type == OBJ_COMMIT) {
                                struct commit *commit = (struct commit *) obj;
                                commit->buffer = NULL;
                        }
                        obj->flags |= FLAG_CHECKED;
                }
        }
}

static int is_delta_type(enum object_type type)
{
        return (type == OBJ_REF_DELTA || type == OBJ_OFS_DELTA);
}

/*
 * This function is part of find_unresolved_deltas(). There are two
 * walkers going in the opposite ways.
 *
 * The first one in find_unresolved_deltas() traverses down from
 * parent node to children, deflating nodes along the way. However,
 * memory for deflated nodes is limited by delta_base_cache_limit, so
 * at some point parent node's deflated content may be freed.
 *
 * The second walker is this function, which goes from current node up
 * to top parent if necessary to deflate the node. In normal
 * situation, its parent node would be already deflated, so it just
 * needs to apply delta.
 *
 * In the worst case scenario, parent node is no longer deflated because
 * we're running out of delta_base_cache_limit; we need to re-deflate
 * parents, possibly up to the top base.
 *
 * All deflated objects here are subject to be freed if we exceed
 * delta_base_cache_limit, just like in find_unresolved_deltas(), we
 * just need to make sure the last node is not freed.
 */
static void *get_base_data(struct base_data *c)
{
        if (!c->data) {
                struct object_entry *obj = c->obj;
                struct base_data **delta = NULL;
                int delta_nr = 0, delta_alloc = 0;

                while (is_delta_type(c->obj->type) && !c->data) {
                        ALLOC_GROW(delta, delta_nr + 1, delta_alloc);
                        delta[delta_nr++] = c;
                        c = c->base;
                }
                if (!delta_nr) {
                        c->data = get_data_from_pack(obj);
                        c->size = obj->size;
                        base_cache_used += c->size;
                        prune_base_data(c);
                }
                for (; delta_nr > 0; delta_nr--) {
                        void *base, *raw;
                        c = delta[delta_nr - 1];
                        obj = c->obj;
                        base = get_base_data(c->base);
                        raw = get_data_from_pack(obj);
                        c->data = patch_delta(
                                base, c->base->size,
                                raw, obj->size,
                                &c->size);
                        free(raw);
                        if (!c->data)
                                bad_object(obj->idx.offset, "failed to apply delta");
                        base_cache_used += c->size;
                        prune_base_data(c);
                }
                free(delta);
        }
        return c->data;
}

static void resolve_delta(struct object_entry *delta_obj,
                          struct base_data *base, struct base_data *result)
{
        void *base_data, *delta_data;

        delta_obj->real_type = base->obj->real_type;
        delta_obj->delta_depth = base->obj->delta_depth + 1;
        if (deepest_delta < delta_obj->delta_depth)
                deepest_delta = delta_obj->delta_depth;
        delta_obj->base_object_no = base->obj - objects;
        delta_data = get_data_from_pack(delta_obj);
        base_data = get_base_data(base);
        result->obj = delta_obj;
        result->data = patch_delta(base_data, base->size,
                                   delta_data, delta_obj->size, &result->size);
        free(delta_data);
        if (!result->data)
                bad_object(delta_obj->idx.offset, "failed to apply delta");
        sha1_object(result->data, result->size, delta_obj->real_type,
                    delta_obj->idx.sha1);
        nr_resolved_deltas++;
}

static struct base_data *find_unresolved_deltas_1(struct base_data *base,
                                                  struct base_data *prev_base)
{
        if (base->ref_last == -1 && base->ofs_last == -1) {
                union delta_base base_spec;

                hashcpy(base_spec.sha1, base->obj->idx.sha1);
                find_delta_children(&base_spec,
                                    &base->ref_first, &base->ref_last, OBJ_REF_DELTA);

                memset(&base_spec, 0, sizeof(base_spec));
                base_spec.offset = base->obj->idx.offset;
                find_delta_children(&base_spec,
                                    &base->ofs_first, &base->ofs_last, OBJ_OFS_DELTA);

                if (base->ref_last == -1 && base->ofs_last == -1) {
                        free(base->data);
                        return NULL;
                }

                link_base_data(prev_base, base);
        }

        if (base->ref_first <= base->ref_last) {
                struct object_entry *child = objects + deltas[base->ref_first].obj_no;
                struct base_data *result = alloc_base_data();

                assert(child->real_type == OBJ_REF_DELTA);
                resolve_delta(child, base, result);
                if (base->ref_first == base->ref_last && base->ofs_last == -1)
                        free_base_data(base);

                base->ref_first++;
                return result;
        }

        if (base->ofs_first <= base->ofs_last) {
                struct object_entry *child = objects + deltas[base->ofs_first].obj_no;
                struct base_data *result = alloc_base_data();

                assert(child->real_type == OBJ_OFS_DELTA);
                resolve_delta(child, base, result);
                if (base->ofs_first == base->ofs_last)
                        free_base_data(base);

                base->ofs_first++;
                return result;
        }

        unlink_base_data(base);
        return NULL;
}

static void find_unresolved_deltas(struct base_data *base)
{
        struct base_data *new_base, *prev_base = NULL;
        for (;;) {
                new_base = find_unresolved_deltas_1(base, prev_base);

                if (new_base) {
                        prev_base = base;
                        base = new_base;
                } else {
                        free(base);
                        base = prev_base;
                        if (!base)
                                return;
                        prev_base = base->base;
                }
        }
}

static int compare_delta_entry(const void *a, const void *b)
{
        const struct delta_entry *delta_a = a;
        const struct delta_entry *delta_b = b;

        /* group by type (ref vs ofs) and then by value (sha-1 or offset) */
        return compare_delta_bases(&delta_a->base, &delta_b->base,
                                   objects[delta_a->obj_no].type,
                                   objects[delta_b->obj_no].type);
}

/* Parse all objects and return the pack content SHA1 hash */
static void parse_pack_objects(unsigned char *sha1)
{
        int i;
        struct delta_entry *delta = deltas;
        struct stat st;

        /*
         * First pass:
         * - find locations of all objects;
         * - calculate SHA1 of all non-delta objects;
         * - remember base (SHA1 or offset) for all deltas.
         */
        if (verbose)
                progress = start_progress(
                                from_stdin ? "Receiving objects" : "Indexing objects",
                                nr_objects);
        for (i = 0; i < nr_objects; i++) {
                struct object_entry *obj = &objects[i];
                void *data = unpack_raw_entry(obj, &delta->base);
                obj->real_type = obj->type;
                if (is_delta_type(obj->type)) {
                        nr_deltas++;
                        delta->obj_no = i;
                        delta++;
                } else
                        sha1_object(data, obj->size, obj->type, obj->idx.sha1);
                free(data);
                display_progress(progress, i+1);
        }
        objects[i].idx.offset = consumed_bytes;
        stop_progress(&progress);

        /* Check pack integrity */
        flush();
        git_SHA1_Final(sha1, &input_ctx);
        if (hashcmp(fill(20), sha1))
                die("pack is corrupted (SHA1 mismatch)");
        use(20);

        /* If input_fd is a file, we should have reached its end now. */
        if (fstat(input_fd, &st))
                die_errno("cannot fstat packfile");
        if (S_ISREG(st.st_mode) &&
                        lseek(input_fd, 0, SEEK_CUR) - input_len != st.st_size)
                die("pack has junk at the end");

        if (!nr_deltas)
                return;

        /* Sort deltas by base SHA1/offset for fast searching */
        qsort(deltas, nr_deltas, sizeof(struct delta_entry),
              compare_delta_entry);

        /*
         * Second pass:
         * - for all non-delta objects, look if it is used as a base for
         *   deltas;
         * - if used as a base, uncompress the object and apply all deltas,
         *   recursively checking if the resulting object is used as a base
         *   for some more deltas.
         */
        if (verbose)
                progress = start_progress("Resolving deltas", nr_deltas);
        for (i = 0; i < nr_objects; i++) {
                struct object_entry *obj = &objects[i];
                struct base_data *base_obj = alloc_base_data();

                if (is_delta_type(obj->type))
                        continue;
                base_obj->obj = obj;
                base_obj->data = NULL;
                find_unresolved_deltas(base_obj);
                display_progress(progress, nr_resolved_deltas);
        }
}

static int write_compressed(struct sha1file *f, void *in, unsigned int size)
{
        git_zstream stream;
        int status;
        unsigned char outbuf[4096];

        memset(&stream, 0, sizeof(stream));
        git_deflate_init(&stream, zlib_compression_level);
        stream.next_in = in;
        stream.avail_in = size;

        do {
                stream.next_out = outbuf;
                stream.avail_out = sizeof(outbuf);
                status = git_deflate(&stream, Z_FINISH);
                sha1write(f, outbuf, sizeof(outbuf) - stream.avail_out);
        } while (status == Z_OK);

        if (status != Z_STREAM_END)
                die("unable to deflate appended object (%d)", status);
        size = stream.total_out;
        git_deflate_end(&stream);
        return size;
}

static struct object_entry *append_obj_to_pack(struct sha1file *f,
                               const unsigned char *sha1, void *buf,
                               unsigned long size, enum object_type type)
{
        struct object_entry *obj = &objects[nr_objects++];
        unsigned char header[10];
        unsigned long s = size;
        int n = 0;
        unsigned char c = (type << 4) | (s & 15);
        s >>= 4;
        while (s) {
                header[n++] = c | 0x80;
                c = s & 0x7f;
                s >>= 7;
        }
        header[n++] = c;
        crc32_begin(f);
        sha1write(f, header, n);
        obj[0].size = size;
        obj[0].hdr_size = n;
        obj[0].type = type;
        obj[0].real_type = type;
        obj[1].idx.offset = obj[0].idx.offset + n;
        obj[1].idx.offset += write_compressed(f, buf, size);
        obj[0].idx.crc32 = crc32_end(f);
        sha1flush(f);
        hashcpy(obj->idx.sha1, sha1);
        return obj;
}

static int delta_pos_compare(const void *_a, const void *_b)
{
        struct delta_entry *a = *(struct delta_entry **)_a;
        struct delta_entry *b = *(struct delta_entry **)_b;
        return a->obj_no - b->obj_no;
}

static void fix_unresolved_deltas(struct sha1file *f, int nr_unresolved)
{
        struct delta_entry **sorted_by_pos;
        int i, n = 0;

        /*
         * Since many unresolved deltas may well be themselves base objects
         * for more unresolved deltas, we really want to include the
         * smallest number of base objects that would cover as much delta
         * as possible by picking the
         * trunc deltas first, allowing for other deltas to resolve without
         * additional base objects.  Since most base objects are to be found
         * before deltas depending on them, a good heuristic is to start
         * resolving deltas in the same order as their position in the pack.
         */
        sorted_by_pos = xmalloc(nr_unresolved * sizeof(*sorted_by_pos));
        for (i = 0; i < nr_deltas; i++) {
                if (objects[deltas[i].obj_no].real_type != OBJ_REF_DELTA)
                        continue;
                sorted_by_pos[n++] = &deltas[i];
        }
        qsort(sorted_by_pos, n, sizeof(*sorted_by_pos), delta_pos_compare);

        for (i = 0; i < n; i++) {
                struct delta_entry *d = sorted_by_pos[i];
                enum object_type type;
                struct base_data *base_obj = alloc_base_data();

                if (objects[d->obj_no].real_type != OBJ_REF_DELTA)
                        continue;
                base_obj->data = read_sha1_file(d->base.sha1, &type, &base_obj->size);
                if (!base_obj->data)
                        continue;

                if (check_sha1_signature(d->base.sha1, base_obj->data,
                                base_obj->size, typename(type)))
                        die("local object %s is corrupt", sha1_to_hex(d->base.sha1));
                base_obj->obj = append_obj_to_pack(f, d->base.sha1,
                                        base_obj->data, base_obj->size, type);
                find_unresolved_deltas(base_obj);
                display_progress(progress, nr_resolved_deltas);
        }
        free(sorted_by_pos);
}

static void final(const char *final_pack_name, const char *curr_pack_name,
                  const char *final_index_name, const char *curr_index_name,
                  const char *keep_name, const char *keep_msg,
                  unsigned char *sha1)
{
        const char *report = "pack";
        char name[PATH_MAX];
        int err;

        if (!from_stdin) {
                close(input_fd);
        } else {
                fsync_or_die(output_fd, curr_pack_name);
                err = close(output_fd);
                if (err)
                        die_errno("error while closing pack file");
        }

        if (keep_msg) {
                int keep_fd, keep_msg_len = strlen(keep_msg);

                if (!keep_name)
                        keep_fd = odb_pack_keep(name, sizeof(name), sha1);
                else
                        keep_fd = open(keep_name, O_RDWR|O_CREAT|O_EXCL, 0600);

                if (keep_fd < 0) {
                        if (errno != EEXIST)
                                die_errno("cannot write keep file '%s'",
                                          keep_name);
                } else {
                        if (keep_msg_len > 0) {
                                write_or_die(keep_fd, keep_msg, keep_msg_len);
                                write_or_die(keep_fd, "\n", 1);
                        }
                        if (close(keep_fd) != 0)
                                die_errno("cannot close written keep file '%s'",
                                    keep_name);
                        report = "keep";
                }
        }

        if (final_pack_name != curr_pack_name) {
                if (!final_pack_name) {
                        snprintf(name, sizeof(name), "%s/pack/pack-%s.pack",
                                 get_object_directory(), sha1_to_hex(sha1));
                        final_pack_name = name;
                }
                if (move_temp_to_file(curr_pack_name, final_pack_name))
                        die("cannot store pack file");
        } else if (from_stdin)
                chmod(final_pack_name, 0444);

        if (final_index_name != curr_index_name) {
                if (!final_index_name) {
                        snprintf(name, sizeof(name), "%s/pack/pack-%s.idx",
                                 get_object_directory(), sha1_to_hex(sha1));
                        final_index_name = name;
                }
                if (move_temp_to_file(curr_index_name, final_index_name))
                        die("cannot store index file");
        } else
                chmod(final_index_name, 0444);

        if (!from_stdin) {
                printf("%s\n", sha1_to_hex(sha1));
        } else {
                char buf[48];
                int len = snprintf(buf, sizeof(buf), "%s\t%s\n",
                                   report, sha1_to_hex(sha1));
                write_or_die(1, buf, len);

                /*
                 * Let's just mimic git-unpack-objects here and write
                 * the last part of the input buffer to stdout.
                 */
                while (input_len) {
                        err = xwrite(1, input_buffer + input_offset, input_len);
                        if (err <= 0)
                                break;
                        input_len -= err;
                        input_offset += err;
                }
        }
}

static int git_index_pack_config(const char *k, const char *v, void *cb)
{
        struct pack_idx_option *opts = cb;

        if (!strcmp(k, "pack.indexversion")) {
                opts->version = git_config_int(k, v);
                if (opts->version > 2)
                        die("bad pack.indexversion=%"PRIu32, opts->version);
                return 0;
        }
        return git_default_config(k, v, cb);
}

static int cmp_uint32(const void *a_, const void *b_)
{
        uint32_t a = *((uint32_t *)a_);
        uint32_t b = *((uint32_t *)b_);

        return (a < b) ? -1 : (a != b);
}

static void read_v2_anomalous_offsets(struct packed_git *p,
                                      struct pack_idx_option *opts)
{
        const uint32_t *idx1, *idx2;
        uint32_t i;

        /* The address of the 4-byte offset table */
        idx1 = (((const uint32_t *)p->index_data)
                + 2 /* 8-byte header */
                + 256 /* fan out */
                + 5 * p->num_objects /* 20-byte SHA-1 table */
                + p->num_objects /* CRC32 table */
                );

        /* The address of the 8-byte offset table */
        idx2 = idx1 + p->num_objects;

        for (i = 0; i < p->num_objects; i++) {
                uint32_t off = ntohl(idx1[i]);
                if (!(off & 0x80000000))
                        continue;
                off = off & 0x7fffffff;
                if (idx2[off * 2])
                        continue;
                /*
                 * The real offset is ntohl(idx2[off * 2]) in high 4
                 * octets, and ntohl(idx2[off * 2 + 1]) in low 4
                 * octets.  But idx2[off * 2] is Zero!!!
                 */
                ALLOC_GROW(opts->anomaly, opts->anomaly_nr + 1, opts->anomaly_alloc);
                opts->anomaly[opts->anomaly_nr++] = ntohl(idx2[off * 2 + 1]);
        }

        if (1 < opts->anomaly_nr)
                qsort(opts->anomaly, opts->anomaly_nr, sizeof(uint32_t), cmp_uint32);
}

static void read_idx_option(struct pack_idx_option *opts, const char *pack_name)
{
        struct packed_git *p = add_packed_git(pack_name, strlen(pack_name), 1);

        if (!p)
                die("Cannot open existing pack file '%s'", pack_name);
        if (open_pack_index(p))
                die("Cannot open existing pack idx file for '%s'", pack_name);

        /* Read the attributes from the existing idx file */
        opts->version = p->index_version;

        if (opts->version == 2)
                read_v2_anomalous_offsets(p, opts);

        /*
         * Get rid of the idx file as we do not need it anymore.
         * NEEDSWORK: extract this bit from free_pack_by_name() in
         * sha1_file.c, perhaps?  It shouldn't matter very much as we
         * know we haven't installed this pack (hence we never have
         * read anything from it).
         */
        close_pack_index(p);
        free(p);
}

static void show_pack_info(int stat_only)
{
        int i, baseobjects = nr_objects - nr_deltas;
        unsigned long *chain_histogram = NULL;

        if (deepest_delta)
                chain_histogram = xcalloc(deepest_delta, sizeof(unsigned long));

        for (i = 0; i < nr_objects; i++) {
                struct object_entry *obj = &objects[i];

                if (is_delta_type(obj->type))
                        chain_histogram[obj->delta_depth - 1]++;
                if (stat_only)
                        continue;
                printf("%s %-6s %lu %lu %"PRIuMAX,
                       sha1_to_hex(obj->idx.sha1),
                       typename(obj->real_type), obj->size,
                       (unsigned long)(obj[1].idx.offset - obj->idx.offset),
                       (uintmax_t)obj->idx.offset);
                if (is_delta_type(obj->type)) {
                        struct object_entry *bobj = &objects[obj->base_object_no];
                        printf(" %u %s", obj->delta_depth, sha1_to_hex(bobj->idx.sha1));
                }
                putchar('\n');
        }

        if (baseobjects)
                printf("non delta: %d object%s\n",
                       baseobjects, baseobjects > 1 ? "s" : "");
        for (i = 0; i < deepest_delta; i++) {
                if (!chain_histogram[i])
                        continue;
                printf("chain length = %d: %lu object%s\n",
                       i + 1,
                       chain_histogram[i],
                       chain_histogram[i] > 1 ? "s" : "");
        }
}

int cmd_index_pack(int argc, const char **argv, const char *prefix)
{
        int i, fix_thin_pack = 0, verify = 0, stat_only = 0, stat = 0;
        const char *curr_pack, *curr_index;
        const char *index_name = NULL, *pack_name = NULL;
        const char *keep_name = NULL, *keep_msg = NULL;
        char *index_name_buf = NULL, *keep_name_buf = NULL;
        struct pack_idx_entry **idx_objects;
        struct pack_idx_option opts;
        unsigned char pack_sha1[20];

        if (argc == 2 && !strcmp(argv[1], "-h"))
                usage(index_pack_usage);

        read_replace_refs = 0;

        reset_pack_idx_option(&opts);
        git_config(git_index_pack_config, &opts);
        if (prefix && chdir(prefix))
                die("Cannot come back to cwd");

        for (i = 1; i < argc; i++) {
                const char *arg = argv[i];

                if (*arg == '-') {
                        if (!strcmp(arg, "--stdin")) {
                                from_stdin = 1;
                        } else if (!strcmp(arg, "--fix-thin")) {
                                fix_thin_pack = 1;
                        } else if (!strcmp(arg, "--strict")) {
                                strict = 1;
                        } else if (!strcmp(arg, "--verify")) {
                                verify = 1;
                        } else if (!strcmp(arg, "--verify-stat")) {
                                verify = 1;
                                stat = 1;
                        } else if (!strcmp(arg, "--verify-stat-only")) {
                                verify = 1;
                                stat = 1;
                                stat_only = 1;
                        } else if (!strcmp(arg, "--keep")) {
                                keep_msg = "";
                        } else if (!prefixcmp(arg, "--keep=")) {
                                keep_msg = arg + 7;
                        } else if (!prefixcmp(arg, "--pack_header=")) {
                                struct pack_header *hdr;
                                char *c;

                                hdr = (struct pack_header *)input_buffer;
                                hdr->hdr_signature = htonl(PACK_SIGNATURE);
                                hdr->hdr_version = htonl(strtoul(arg + 14, &c, 10));
                                if (*c != ',')
                                        die("bad %s", arg);
                                hdr->hdr_entries = htonl(strtoul(c + 1, &c, 10));
                                if (*c)
                                        die("bad %s", arg);
                                input_len = sizeof(*hdr);
                        } else if (!strcmp(arg, "-v")) {
                                verbose = 1;
                        } else if (!strcmp(arg, "-o")) {
                                if (index_name || (i+1) >= argc)
                                        usage(index_pack_usage);
                                index_name = argv[++i];
                        } else if (!prefixcmp(arg, "--index-version=")) {
                                char *c;
                                opts.version = strtoul(arg + 16, &c, 10);
                                if (opts.version > 2)
                                        die("bad %s", arg);
                                if (*c == ',')
                                        opts.off32_limit = strtoul(c+1, &c, 0);
                                if (*c || opts.off32_limit & 0x80000000)
                                        die("bad %s", arg);
                        } else
                                usage(index_pack_usage);
                        continue;
                }

                if (pack_name)
                        usage(index_pack_usage);
                pack_name = arg;
        }

        if (!pack_name && !from_stdin)
                usage(index_pack_usage);
        if (fix_thin_pack && !from_stdin)
                die("--fix-thin cannot be used without --stdin");
        if (!index_name && pack_name) {
                int len = strlen(pack_name);
                if (!has_extension(pack_name, ".pack"))
                        die("packfile name '%s' does not end with '.pack'",
                            pack_name);
                index_name_buf = xmalloc(len);
                memcpy(index_name_buf, pack_name, len - 5);
                strcpy(index_name_buf + len - 5, ".idx");
                index_name = index_name_buf;
        }
        if (keep_msg && !keep_name && pack_name) {
                int len = strlen(pack_name);
                if (!has_extension(pack_name, ".pack"))
                        die("packfile name '%s' does not end with '.pack'",
                            pack_name);
                keep_name_buf = xmalloc(len);
                memcpy(keep_name_buf, pack_name, len - 5);
                strcpy(keep_name_buf + len - 5, ".keep");
                keep_name = keep_name_buf;
        }
        if (verify) {
                if (!index_name)
                        die("--verify with no packfile name given");
                read_idx_option(&opts, index_name);
                opts.flags |= WRITE_IDX_VERIFY | WRITE_IDX_STRICT;
        }
        if (strict)
                opts.flags |= WRITE_IDX_STRICT;

        curr_pack = open_pack_file(pack_name);
        parse_pack_header();
        objects = xcalloc(nr_objects + 1, sizeof(struct object_entry));
        deltas = xcalloc(nr_objects, sizeof(struct delta_entry));
        parse_pack_objects(pack_sha1);
        if (nr_deltas == nr_resolved_deltas) {
                stop_progress(&progress);
                /* Flush remaining pack final 20-byte SHA1. */
                flush();
        } else {
                if (fix_thin_pack) {
                        struct sha1file *f;
                        unsigned char read_sha1[20], tail_sha1[20];
                        char msg[48];
                        int nr_unresolved = nr_deltas - nr_resolved_deltas;
                        int nr_objects_initial = nr_objects;
                        if (nr_unresolved <= 0)
                                die("confusion beyond insanity");
                        objects = xrealloc(objects,
                                           (nr_objects + nr_unresolved + 1)
                                           * sizeof(*objects));
                        f = sha1fd(output_fd, curr_pack);
                        fix_unresolved_deltas(f, nr_unresolved);
                        sprintf(msg, "completed with %d local objects",
                                nr_objects - nr_objects_initial);
                        stop_progress_msg(&progress, msg);
                        sha1close(f, tail_sha1, 0);
                        hashcpy(read_sha1, pack_sha1);
                        fixup_pack_header_footer(output_fd, pack_sha1,
                                                 curr_pack, nr_objects,
                                                 read_sha1, consumed_bytes-20);
                        if (hashcmp(read_sha1, tail_sha1) != 0)
                                die("Unexpected tail checksum for %s "
                                    "(disk corruption?)", curr_pack);
                }
                if (nr_deltas != nr_resolved_deltas)
                        die("pack has %d unresolved deltas",
                            nr_deltas - nr_resolved_deltas);
        }
        free(deltas);
        if (strict)
                check_objects();

        if (stat)
                show_pack_info(stat_only);

        idx_objects = xmalloc((nr_objects) * sizeof(struct pack_idx_entry *));
        for (i = 0; i < nr_objects; i++)
                idx_objects[i] = &objects[i].idx;
        curr_index = write_idx_file(index_name, idx_objects, nr_objects, &opts, pack_sha1);
        free(idx_objects);

        if (!verify)
                final(pack_name, curr_pack,
                      index_name, curr_index,
                      keep_name, keep_msg,
                      pack_sha1);
        else
                close(input_fd);
        free(objects);
        free(index_name_buf);
        free(keep_name_buf);
        if (pack_name == NULL)
                free((void *) curr_pack);
        if (index_name == NULL)
                free((void *) curr_index);

        return 0;
}