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 sha1file *f, 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 sha1flush(struct sha1file *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 sha1close(struct sha1file *f, unsigned char *result, unsigned int flags)
  57 {
  58         int fd;
  59
  60         sha1flush(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 int sha1write(struct sha1file *f, 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                 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         return 0;
 120 }
 121
 122 struct sha1file *sha1fd(int fd, const char *name)
 123 {
 124         return sha1fd_throughput(fd, name, NULL);
 125 }
 126
 127 struct sha1file *sha1fd_check(const char *name)
 128 {
 129         int sink, check;
 130         struct sha1file *f;
 131
 132         sink = open("/dev/null", O_WRONLY);
 133         if (sink < 0)
 134                 return NULL;
 135         check = open(name, O_RDONLY);
 136         if (check < 0) {
 137                 int saved_errno = errno;
 138                 close(sink);
 139                 errno = saved_errno;
 140                 return NULL;
 141         }
 142         f = sha1fd(sink, name);
 143         f->check_fd = check;
 144         return f;
 145 }
 146
 147 struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp)
 148 {
 149         struct sha1file *f = xmalloc(sizeof(*f));
 150         f->fd = fd;
 151         f->check_fd = -1;
 152         f->offset = 0;
 153         f->total = 0;
 154         f->tp = tp;
 155         f->name = name;
 156         f->do_crc = 0;
 157         git_SHA1_Init(&f->ctx);
 158         return f;
 159 }
 160
 161 void sha1file_checkpoint(struct sha1file *f, struct sha1file_checkpoint *checkpoint)
 162 {
 163         sha1flush(f);
 164         checkpoint->offset = f->total;
 165         checkpoint->ctx = f->ctx;
 166 }
 167
 168 int sha1file_truncate(struct sha1file *f, struct sha1file_checkpoint *checkpoint)
 169 {
 170         off_t offset = checkpoint->offset;
 171
 172         if (ftruncate(f->fd, offset) ||
 173             lseek(f->fd, offset, SEEK_SET) != offset)
 174                 return -1;
 175         f->total = offset;
 176         f->ctx = checkpoint->ctx;
 177         f->offset = 0; /* sha1flush() was called in checkpoint */
 178         return 0;
 179 }
 180
 181 void crc32_begin(struct sha1file *f)
 182 {
 183         f->crc32 = crc32(0, NULL, 0);
 184         f->do_crc = 1;
 185 }
 186
 187 uint32_t crc32_end(struct sha1file *f)
 188 {
 189         f->do_crc = 0;
 190         return f->crc32;
 191 }