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 "csum-file.h"
  12
  13 static int sha1flush(struct sha1file *f, unsigned int count)
  14 {
  15         void *buf = f->buffer;
  16
  17         for (;;) {
  18                 int ret = write(f->fd, buf, count);
  19                 if (ret > 0) {
  20                         buf += ret;
  21                         count -= ret;
  22                         if (count)
  23                                 continue;
  24                         return 0;
  25                 }
  26                 if (!ret)
  27                         die("sha1 file '%s' write error. Out of diskspace", f->name);
  28                 if (errno == EAGAIN || errno == EINTR)
  29                         continue;
  30                 die("sha1 file '%s' write error (%s)", f->name, strerror(errno));
  31         }
  32 }
  33
  34 int sha1close(struct sha1file *f, unsigned char *result, int update)
  35 {
  36         unsigned offset = f->offset;
  37         if (offset) {
  38                 SHA1_Update(&f->ctx, f->buffer, offset);
  39                 sha1flush(f, offset);
  40         }
  41         SHA1_Final(f->buffer, &f->ctx);
  42         if (result)
  43                 memcpy(result, f->buffer, 20);
  44         if (update)
  45                 sha1flush(f, 20);
  46         if (close(f->fd))
  47                 die("%s: sha1 file error on close (%s)", f->name, strerror(errno));
  48         return 0;
  49 }
  50
  51 int sha1write(struct sha1file *f, void *buf, unsigned int count)
  52 {
  53         while (count) {
  54                 unsigned offset = f->offset;
  55                 unsigned left = sizeof(f->buffer) - offset;
  56                 unsigned nr = count > left ? left : count;
  57
  58                 memcpy(f->buffer + offset, buf, nr);
  59                 count -= nr;
  60                 offset += nr;
  61                 left -= nr;
  62                 if (!left) {
  63                         SHA1_Update(&f->ctx, f->buffer, offset);
  64                         sha1flush(f, offset);
  65                         offset = 0;
  66                 }
  67                 f->offset = offset;
  68         }
  69         return 0;
  70 }
  71
  72 struct sha1file *sha1create(const char *fmt, ...)
  73 {
  74         struct sha1file *f;
  75         unsigned len;
  76         va_list arg;
  77         int fd;
  78
  79         f = xmalloc(sizeof(*f));
  80
  81         va_start(arg, fmt);
  82         len = vsnprintf(f->name, sizeof(f->name), fmt, arg);
  83         va_end(arg);
  84         if (len >= PATH_MAX)
  85                 die("you wascally wabbit, you");
  86         f->namelen = len;
  87
  88         fd = open(f->name, O_CREAT | O_EXCL | O_WRONLY, 0644);
  89         if (fd < 0)
  90                 die("unable to open %s (%s)", f->name, strerror(errno));
  91         f->fd = fd;
  92         f->error = 0;
  93         f->offset = 0;
  94         SHA1_Init(&f->ctx);
  95         return f;
  96 }
  97
  98 int sha1write_compressed(struct sha1file *f, void *in, unsigned int size)
  99 {
 100         z_stream stream;
 101         unsigned long maxsize;
 102         void *out;
 103
 104         memset(&stream, 0, sizeof(stream));
 105         deflateInit(&stream, Z_DEFAULT_COMPRESSION);
 106         maxsize = deflateBound(&stream, size);
 107         out = xmalloc(maxsize);
 108
 109         /* Compress it */
 110         stream.next_in = in;
 111         stream.avail_in = size;
 112
 113         stream.next_out = out;
 114         stream.avail_out = maxsize;
 115
 116         while (deflate(&stream, Z_FINISH) == Z_OK)
 117                 /* nothing */;
 118         deflateEnd(&stream);
 119
 120         size = stream.total_out;
 121         sha1write(f, out, size);
 122         free(out);
 123         return size;
 124 }
 125
 126