chunk-format.c

   1 #include "cache.h"
   2 #include "chunk-format.h"
   3 #include "csum-file.h"
   4
   5 /*
   6  * When writing a chunk-based file format, collect the chunks in
   7  * an array of chunk_info structs. The size stores the _expected_
   8  * amount of data that will be written by write_fn.
   9  */
  10 struct chunk_info {
  11         uint32_t id;
  12         uint64_t size;
  13         chunk_write_fn write_fn;
  14
  15         const void *start;
  16 };
  17
  18 struct chunkfile {
  19         struct hashfile *f;
  20
  21         struct chunk_info *chunks;
  22         size_t chunks_nr;
  23         size_t chunks_alloc;
  24 };
  25
  26 struct chunkfile *init_chunkfile(struct hashfile *f)
  27 {
  28         struct chunkfile *cf = xcalloc(1, sizeof(*cf));
  29         cf->f = f;
  30         return cf;
  31 }
  32
  33 void free_chunkfile(struct chunkfile *cf)
  34 {
  35         if (!cf)
  36                 return;
  37         free(cf->chunks);
  38         free(cf);
  39 }
  40
  41 int get_num_chunks(struct chunkfile *cf)
  42 {
  43         return cf->chunks_nr;
  44 }
  45
  46 void add_chunk(struct chunkfile *cf,
  47                uint32_t id,
  48                size_t size,
  49                chunk_write_fn fn)
  50 {
  51         ALLOC_GROW(cf->chunks, cf->chunks_nr + 1, cf->chunks_alloc);
  52
  53         cf->chunks[cf->chunks_nr].id = id;
  54         cf->chunks[cf->chunks_nr].write_fn = fn;
  55         cf->chunks[cf->chunks_nr].size = size;
  56         cf->chunks_nr++;
  57 }
  58
  59 int write_chunkfile(struct chunkfile *cf, void *data)
  60 {
  61         int i;
  62         uint64_t cur_offset = hashfile_total(cf->f);
  63
  64         /* Add the table of contents to the current offset */
  65         cur_offset += (cf->chunks_nr + 1) * CHUNK_TOC_ENTRY_SIZE;
  66
  67         for (i = 0; i < cf->chunks_nr; i++) {
  68                 hashwrite_be32(cf->f, cf->chunks[i].id);
  69                 hashwrite_be64(cf->f, cur_offset);
  70
  71                 cur_offset += cf->chunks[i].size;
  72         }
  73
  74         /* Trailing entry marks the end of the chunks */
  75         hashwrite_be32(cf->f, 0);
  76         hashwrite_be64(cf->f, cur_offset);
  77
  78         for (i = 0; i < cf->chunks_nr; i++) {
  79                 off_t start_offset = hashfile_total(cf->f);
  80                 int result = cf->chunks[i].write_fn(cf->f, data);
  81
  82                 if (result)
  83                         return result;
  84
  85                 if (hashfile_total(cf->f) - start_offset != cf->chunks[i].size)
  86                         BUG("expected to write %"PRId64" bytes to chunk %"PRIx32", but wrote %"PRId64" instead",
  87                             cf->chunks[i].size, cf->chunks[i].id,
  88                             hashfile_total(cf->f) - start_offset);
  89         }
  90
  91         return 0;
  92 }
  93
  94 int read_table_of_contents(struct chunkfile *cf,
  95                            const unsigned char *mfile,
  96                            size_t mfile_size,
  97                            uint64_t toc_offset,
  98                            int toc_length)
  99 {
 100         int i;
 101         uint32_t chunk_id;
 102         const unsigned char *table_of_contents = mfile + toc_offset;
 103
 104         ALLOC_GROW(cf->chunks, toc_length, cf->chunks_alloc);
 105
 106         while (toc_length--) {
 107                 uint64_t chunk_offset, next_chunk_offset;
 108
 109                 chunk_id = get_be32(table_of_contents);
 110                 chunk_offset = get_be64(table_of_contents + 4);
 111
 112                 if (!chunk_id) {
 113                         error(_("terminating chunk id appears earlier than expected"));
 114                         return 1;
 115                 }
 116
 117                 table_of_contents += CHUNK_TOC_ENTRY_SIZE;
 118                 next_chunk_offset = get_be64(table_of_contents + 4);
 119
 120                 if (next_chunk_offset < chunk_offset ||
 121                     next_chunk_offset > mfile_size - the_hash_algo->rawsz) {
 122                         error(_("improper chunk offset(s) %"PRIx64" and %"PRIx64""),
 123                               chunk_offset, next_chunk_offset);
 124                         return -1;
 125                 }
 126
 127                 for (i = 0; i < cf->chunks_nr; i++) {
 128                         if (cf->chunks[i].id == chunk_id) {
 129                                 error(_("duplicate chunk ID %"PRIx32" found"),
 130                                         chunk_id);
 131                                 return -1;
 132                         }
 133                 }
 134
 135                 cf->chunks[cf->chunks_nr].id = chunk_id;
 136                 cf->chunks[cf->chunks_nr].start = mfile + chunk_offset;
 137                 cf->chunks[cf->chunks_nr].size = next_chunk_offset - chunk_offset;
 138                 cf->chunks_nr++;
 139         }
 140
 141         chunk_id = get_be32(table_of_contents);
 142         if (chunk_id) {
 143                 error(_("final chunk has non-zero id %"PRIx32""), chunk_id);
 144                 return -1;
 145         }
 146
 147         return 0;
 148 }
 149
 150 static int pair_chunk_fn(const unsigned char *chunk_start,
 151                          size_t chunk_size,
 152                          void *data)
 153 {
 154         const unsigned char **p = data;
 155         *p = chunk_start;
 156         return 0;
 157 }
 158
 159 int pair_chunk(struct chunkfile *cf,
 160                uint32_t chunk_id,
 161                const unsigned char **p)
 162 {
 163         return read_chunk(cf, chunk_id, pair_chunk_fn, p);
 164 }
 165
 166 int read_chunk(struct chunkfile *cf,
 167                uint32_t chunk_id,
 168                chunk_read_fn fn,
 169                void *data)
 170 {
 171         int i;
 172
 173         for (i = 0; i < cf->chunks_nr; i++) {
 174                 if (cf->chunks[i].id == chunk_id)
 175                         return fn(cf->chunks[i].start, cf->chunks[i].size, data);
 176         }
 177
 178         return CHUNK_NOT_FOUND;
 179 }