csum-file.c

   1 /*
   2  * csum-file.c
   3  *
   4  * Copyright (C) 2005 Linus Torvalds
   5  *
   6  * Simple file write infrastructure for writing SHA1-summed
   7  * files. Useful when you write a file that you want to be
   8  * able to verify hasn't been messed with afterwards.
   9  */
  10 #include "cache.h"
  11 #include "progress.h"
  12 #include "csum-file.h"
  13
  14 static void flush(struct hashfile *f, const void *buf, unsigned int count)
  15 {
  16         if (0 <= f->check_fd && count)  {
  17                 unsigned char check_buffer[8192];
  18                 ssize_t ret = read_in_full(f->check_fd, check_buffer, count);
  19
  20                 if (ret < 0)
  21                         die_errno("%s: sha1 file read error", f->name);
  22                 if (ret != count)
  23                         die("%s: sha1 file truncated", f->name);
  24                 if (memcmp(buf, check_buffer, count))
  25                         die("sha1 file '%s' validation error", f->name);
  26         }
  27
  28         for (;;) {
  29                 int ret = xwrite(f->fd, buf, count);
  30                 if (ret > 0) {
  31                         f->total += ret;
  32                         display_throughput(f->tp, f->total);
  33                         buf = (char *) buf + ret;
  34                         count -= ret;
  35                         if (count)
  36                                 continue;
  37                         return;
  38                 }
  39                 if (!ret)
  40                         die("sha1 file '%s' write error. Out of diskspace", f->name);
  41                 die_errno("sha1 file '%s' write error", f->name);
  42         }
  43 }
  44
  45 void hashflush(struct hashfile *f)
  46 {
  47         unsigned offset = f->offset;
  48
  49         if (offset) {
  50                 the_hash_algo->update_fn(&f->ctx, f->buffer, offset);
  51                 flush(f, f->buffer, offset);
  52                 f->offset = 0;
  53         }
  54 }
  55
  56 int finalize_hashfile(struct hashfile *f, unsigned char *result, unsigned int flags)
  57 {
  58         int fd;
  59
  60         hashflush(f);
  61         the_hash_algo->final_fn(f->buffer, &f->ctx);
  62         if (result)
  63                 hashcpy(result, f->buffer);
  64         if (flags & CSUM_HASH_IN_STREAM)
  65                 flush(f, f->buffer, the_hash_algo->rawsz);
  66         if (flags & CSUM_FSYNC)
  67                 fsync_or_die(f->fd, f->name);
  68         if (flags & CSUM_CLOSE) {
  69                 if (close(f->fd))
  70                         die_errno("%s: sha1 file error on close", f->name);
  71                 fd = 0;
  72         } else
  73                 fd = f->fd;
  74         if (0 <= f->check_fd) {
  75                 char discard;
  76                 int cnt = read_in_full(f->check_fd, &discard, 1);
  77                 if (cnt < 0)
  78                         die_errno("%s: error when reading the tail of sha1 file",
  79                                   f->name);
  80                 if (cnt)
  81                         die("%s: sha1 file has trailing garbage", f->name);
  82                 if (close(f->check_fd))
  83                         die_errno("%s: sha1 file error on close", f->name);
  84         }
  85         free(f);
  86         return fd;
  87 }
  88
  89 void hashwrite(struct hashfile *f, const void *buf, unsigned int count)
  90 {
  91         while (count) {
  92                 unsigned left = sizeof(f->buffer) - f->offset;
  93                 unsigned nr = count > left ? left : count;
  94
  95                 if (f->do_crc)
  96                         f->crc32 = crc32(f->crc32, buf, nr);
  97
  98                 if (nr == sizeof(f->buffer)) {
  99                         /*
 100                          * Flush a full batch worth of data directly
 101                          * from the input, skipping the memcpy() to
 102                          * the hashfile's buffer. In this block,
 103                          * f->offset is necessarily zero.
 104                          */
 105                         the_hash_algo->update_fn(&f->ctx, buf, nr);
 106                         flush(f, buf, nr);
 107                 } else {
 108                         /*
 109                          * Copy to the hashfile's buffer, flushing only
 110                          * if it became full.
 111                          */
 112                         memcpy(f->buffer + f->offset, buf, nr);
 113                         f->offset += nr;
 114                         left -= nr;
 115                         if (!left)
 116                                 hashflush(f);
 117                 }
 118
 119                 count -= nr;
 120                 buf = (char *) buf + nr;
 121         }
 122 }
 123
 124 struct hashfile *hashfd(int fd, const char *name)
 125 {
 126         return hashfd_throughput(fd, name, NULL);
 127 }
 128
 129 struct hashfile *hashfd_check(const char *name)
 130 {
 131         int sink, check;
 132         struct hashfile *f;
 133
 134         sink = open("/dev/null", O_WRONLY);
 135         if (sink < 0)
 136                 die_errno("unable to open /dev/null");
 137         check = open(name, O_RDONLY);
 138         if (check < 0)
 139                 die_errno("unable to open '%s'", name);
 140         f = hashfd(sink, name);
 141         f->check_fd = check;
 142         return f;
 143 }
 144
 145 struct hashfile *hashfd_throughput(int fd, const char *name, struct progress *tp)
 146 {
 147         struct hashfile *f = xmalloc(sizeof(*f));
 148         f->fd = fd;
 149         f->check_fd = -1;
 150         f->offset = 0;
 151         f->total = 0;
 152         f->tp = tp;
 153         f->name = name;
 154         f->do_crc = 0;
 155         the_hash_algo->init_fn(&f->ctx);
 156         return f;
 157 }
 158
 159 void hashfile_checkpoint(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
 160 {
 161         hashflush(f);
 162         checkpoint->offset = f->total;
 163         the_hash_algo->clone_fn(&checkpoint->ctx, &f->ctx);
 164 }
 165
 166 int hashfile_truncate(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
 167 {
 168         off_t offset = checkpoint->offset;
 169
 170         if (ftruncate(f->fd, offset) ||
 171             lseek(f->fd, offset, SEEK_SET) != offset)
 172                 return -1;
 173         f->total = offset;
 174         f->ctx = checkpoint->ctx;
 175         f->offset = 0; /* hashflush() was called in checkpoint */
 176         return 0;
 177 }
 178
 179 void crc32_begin(struct hashfile *f)
 180 {
 181         f->crc32 = crc32(0, NULL, 0);
 182         f->do_crc = 1;
 183 }
 184
 185 uint32_t crc32_end(struct hashfile *f)
 186 {
 187         f->do_crc = 0;
 188         return f->crc32;
 189 }