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                 git_SHA1_Update(&f->ctx, f->buffer, offset);
  51                 flush(f, f->buffer, offset);
  52                 f->offset = 0;
  53         }
  54 }
  55
  56 int hashclose(struct hashfile *f, unsigned char *result, unsigned int flags)
  57 {
  58         int fd;
  59
  60         hashflush(f);
  61         git_SHA1_Final(f->buffer, &f->ctx);
  62         if (result)
  63                 hashcpy(result, f->buffer);
  64         if (flags & (CSUM_CLOSE | CSUM_FSYNC)) {
  65                 /* write checksum and close fd */
  66                 flush(f, f->buffer, 20);
  67                 if (flags & CSUM_FSYNC)
  68                         fsync_or_die(f->fd, f->name);
  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 offset = f->offset;
  93                 unsigned left = sizeof(f->buffer) - offset;
  94                 unsigned nr = count > left ? left : count;
  95                 const void *data;
  96
  97                 if (f->do_crc)
  98                         f->crc32 = crc32(f->crc32, buf, nr);
  99
 100                 if (nr == sizeof(f->buffer)) {
 101                         /* process full buffer directly without copy */
 102                         data = buf;
 103                 } else {
 104                         memcpy(f->buffer + offset, buf, nr);
 105                         data = f->buffer;
 106                 }
 107
 108                 count -= nr;
 109                 offset += nr;
 110                 buf = (char *) buf + nr;
 111                 left -= nr;
 112                 if (!left) {
 113                         git_SHA1_Update(&f->ctx, data, offset);
 114                         flush(f, data, offset);
 115                         offset = 0;
 116                 }
 117                 f->offset = offset;
 118         }
 119 }
 120
 121 struct hashfile *hashfd(int fd, const char *name)
 122 {
 123         return hashfd_throughput(fd, name, NULL);
 124 }
 125
 126 struct hashfile *hashfd_check(const char *name)
 127 {
 128         int sink, check;
 129         struct hashfile *f;
 130
 131         sink = open("/dev/null", O_WRONLY);
 132         if (sink < 0)
 133                 die_errno("unable to open /dev/null");
 134         check = open(name, O_RDONLY);
 135         if (check < 0)
 136                 die_errno("unable to open '%s'", name);
 137         f = hashfd(sink, name);
 138         f->check_fd = check;
 139         return f;
 140 }
 141
 142 struct hashfile *hashfd_throughput(int fd, const char *name, struct progress *tp)
 143 {
 144         struct hashfile *f = xmalloc(sizeof(*f));
 145         f->fd = fd;
 146         f->check_fd = -1;
 147         f->offset = 0;
 148         f->total = 0;
 149         f->tp = tp;
 150         f->name = name;
 151         f->do_crc = 0;
 152         git_SHA1_Init(&f->ctx);
 153         return f;
 154 }
 155
 156 void hashfile_checkpoint(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
 157 {
 158         hashflush(f);
 159         checkpoint->offset = f->total;
 160         checkpoint->ctx = f->ctx;
 161 }
 162
 163 int hashfile_truncate(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
 164 {
 165         off_t offset = checkpoint->offset;
 166
 167         if (ftruncate(f->fd, offset) ||
 168             lseek(f->fd, offset, SEEK_SET) != offset)
 169                 return -1;
 170         f->total = offset;
 171         f->ctx = checkpoint->ctx;
 172         f->offset = 0; /* hashflush() was called in checkpoint */
 173         return 0;
 174 }
 175
 176 void crc32_begin(struct hashfile *f)
 177 {
 178         f->crc32 = crc32(0, NULL, 0);
 179         f->do_crc = 1;
 180 }
 181
 182 uint32_t crc32_end(struct hashfile *f)
 183 {
 184         f->do_crc = 0;
 185         return f->crc32;
 186 }