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
  11 #define USE_THE_REPOSITORY_VARIABLE
  12
  13 #include "git-compat-util.h"
  14 #include "progress.h"
  15 #include "csum-file.h"
  16 #include "hash.h"
  17
  18 static void verify_buffer_or_die(struct hashfile *f,
  19                                  const void *buf,
  20                                  unsigned int count)
  21 {
  22         ssize_t ret = read_in_full(f->check_fd, f->check_buffer, count);
  23
  24         if (ret < 0)
  25                 die_errno("%s: sha1 file read error", f->name);
  26         if (ret != count)
  27                 die("%s: sha1 file truncated", f->name);
  28         if (memcmp(buf, f->check_buffer, count))
  29                 die("sha1 file '%s' validation error", f->name);
  30 }
  31
  32 static void flush(struct hashfile *f, const void *buf, unsigned int count)
  33 {
  34         if (0 <= f->check_fd && count)
  35                 verify_buffer_or_die(f, buf, count);
  36
  37         if (write_in_full(f->fd, buf, count) < 0) {
  38                 if (errno == ENOSPC)
  39                         die("sha1 file '%s' write error. Out of diskspace", f->name);
  40                 die_errno("sha1 file '%s' write error", f->name);
  41         }
  42
  43         f->total += count;
  44         display_throughput(f->tp, f->total);
  45 }
  46
  47 void hashflush(struct hashfile *f)
  48 {
  49         unsigned offset = f->offset;
  50
  51         if (offset) {
  52                 if (!f->skip_hash)
  53                         the_hash_algo->update_fn(&f->ctx, f->buffer, offset);
  54                 flush(f, f->buffer, offset);
  55                 f->offset = 0;
  56         }
  57 }
  58
  59 static void free_hashfile(struct hashfile *f)
  60 {
  61         free(f->buffer);
  62         free(f->check_buffer);
  63         free(f);
  64 }
  65
  66 int finalize_hashfile(struct hashfile *f, unsigned char *result,
  67                       enum fsync_component component, unsigned int flags)
  68 {
  69         int fd;
  70
  71         hashflush(f);
  72
  73         if (f->skip_hash)
  74                 hashclr(f->buffer, the_repository->hash_algo);
  75         else
  76                 the_hash_algo->final_fn(f->buffer, &f->ctx);
  77
  78         if (result)
  79                 hashcpy(result, f->buffer, the_repository->hash_algo);
  80         if (flags & CSUM_HASH_IN_STREAM)
  81                 flush(f, f->buffer, the_hash_algo->rawsz);
  82         if (flags & CSUM_FSYNC)
  83                 fsync_component_or_die(component, f->fd, f->name);
  84         if (flags & CSUM_CLOSE) {
  85                 if (close(f->fd))
  86                         die_errno("%s: sha1 file error on close", f->name);
  87                 fd = 0;
  88         } else
  89                 fd = f->fd;
  90         if (0 <= f->check_fd) {
  91                 char discard;
  92                 int cnt = read_in_full(f->check_fd, &discard, 1);
  93                 if (cnt < 0)
  94                         die_errno("%s: error when reading the tail of sha1 file",
  95                                   f->name);
  96                 if (cnt)
  97                         die("%s: sha1 file has trailing garbage", f->name);
  98                 if (close(f->check_fd))
  99                         die_errno("%s: sha1 file error on close", f->name);
 100         }
 101         free_hashfile(f);
 102         return fd;
 103 }
 104
 105 void discard_hashfile(struct hashfile *f)
 106 {
 107         if (0 <= f->check_fd)
 108                 close(f->check_fd);
 109         if (0 <= f->fd)
 110                 close(f->fd);
 111         free_hashfile(f);
 112 }
 113
 114 void hashwrite(struct hashfile *f, const void *buf, unsigned int count)
 115 {
 116         while (count) {
 117                 unsigned left = f->buffer_len - f->offset;
 118                 unsigned nr = count > left ? left : count;
 119
 120                 if (f->do_crc)
 121                         f->crc32 = crc32(f->crc32, buf, nr);
 122
 123                 if (nr == f->buffer_len) {
 124                         /*
 125                          * Flush a full batch worth of data directly
 126                          * from the input, skipping the memcpy() to
 127                          * the hashfile's buffer. In this block,
 128                          * f->offset is necessarily zero.
 129                          */
 130                         if (!f->skip_hash)
 131                                 the_hash_algo->update_fn(&f->ctx, buf, nr);
 132                         flush(f, buf, nr);
 133                 } else {
 134                         /*
 135                          * Copy to the hashfile's buffer, flushing only
 136                          * if it became full.
 137                          */
 138                         memcpy(f->buffer + f->offset, buf, nr);
 139                         f->offset += nr;
 140                         left -= nr;
 141                         if (!left)
 142                                 hashflush(f);
 143                 }
 144
 145                 count -= nr;
 146                 buf = (char *) buf + nr;
 147         }
 148 }
 149
 150 struct hashfile *hashfd_check(const char *name)
 151 {
 152         int sink, check;
 153         struct hashfile *f;
 154
 155         sink = xopen("/dev/null", O_WRONLY);
 156         check = xopen(name, O_RDONLY);
 157         f = hashfd(sink, name);
 158         f->check_fd = check;
 159         f->check_buffer = xmalloc(f->buffer_len);
 160
 161         return f;
 162 }
 163
 164 static struct hashfile *hashfd_internal(int fd, const char *name,
 165                                         struct progress *tp,
 166                                         size_t buffer_len)
 167 {
 168         struct hashfile *f = xmalloc(sizeof(*f));
 169         f->fd = fd;
 170         f->check_fd = -1;
 171         f->offset = 0;
 172         f->total = 0;
 173         f->tp = tp;
 174         f->name = name;
 175         f->do_crc = 0;
 176         f->skip_hash = 0;
 177         the_hash_algo->init_fn(&f->ctx);
 178
 179         f->buffer_len = buffer_len;
 180         f->buffer = xmalloc(buffer_len);
 181         f->check_buffer = NULL;
 182
 183         return f;
 184 }
 185
 186 struct hashfile *hashfd(int fd, const char *name)
 187 {
 188         /*
 189          * Since we are not going to use a progress meter to
 190          * measure the rate of data passing through this hashfile,
 191          * use a larger buffer size to reduce fsync() calls.
 192          */
 193         return hashfd_internal(fd, name, NULL, 128 * 1024);
 194 }
 195
 196 struct hashfile *hashfd_throughput(int fd, const char *name, struct progress *tp)
 197 {
 198         /*
 199          * Since we are expecting to report progress of the
 200          * write into this hashfile, use a smaller buffer
 201          * size so the progress indicators arrive at a more
 202          * frequent rate.
 203          */
 204         return hashfd_internal(fd, name, tp, 8 * 1024);
 205 }
 206
 207 void hashfile_checkpoint(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
 208 {
 209         hashflush(f);
 210         checkpoint->offset = f->total;
 211         the_hash_algo->clone_fn(&checkpoint->ctx, &f->ctx);
 212 }
 213
 214 int hashfile_truncate(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
 215 {
 216         off_t offset = checkpoint->offset;
 217
 218         if (ftruncate(f->fd, offset) ||
 219             lseek(f->fd, offset, SEEK_SET) != offset)
 220                 return -1;
 221         f->total = offset;
 222         the_hash_algo->clone_fn(&f->ctx, &checkpoint->ctx);
 223         f->offset = 0; /* hashflush() was called in checkpoint */
 224         return 0;
 225 }
 226
 227 void crc32_begin(struct hashfile *f)
 228 {
 229         f->crc32 = crc32(0, NULL, 0);
 230         f->do_crc = 1;
 231 }
 232
 233 uint32_t crc32_end(struct hashfile *f)
 234 {
 235         f->do_crc = 0;
 236         return f->crc32;
 237 }
 238
 239 int hashfile_checksum_valid(const unsigned char *data, size_t total_len)
 240 {
 241         unsigned char got[GIT_MAX_RAWSZ];
 242         git_hash_ctx ctx;
 243         size_t data_len = total_len - the_hash_algo->rawsz;
 244
 245         if (total_len < the_hash_algo->rawsz)
 246                 return 0; /* say "too short"? */
 247
 248         the_hash_algo->init_fn(&ctx);
 249         the_hash_algo->update_fn(&ctx, data, data_len);
 250         the_hash_algo->final_fn(got, &ctx);
 251
 252         return hasheq(got, data + data_len, the_repository->hash_algo);
 253 }