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 = xwrite(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                 die("sha1 file '%s' write error (%s)", f->name, strerror(errno));
  29         }
  30 }
  31
  32 int sha1close(struct sha1file *f, unsigned char *result, int update)
  33 {
  34         unsigned offset = f->offset;
  35         if (offset) {
  36                 SHA1_Update(&f->ctx, f->buffer, offset);
  37                 sha1flush(f, offset);
  38         }
  39         SHA1_Final(f->buffer, &f->ctx);
  40         if (result)
  41                 memcpy(result, f->buffer, 20);
  42         if (update)
  43                 sha1flush(f, 20);
  44         if (close(f->fd))
  45                 die("%s: sha1 file error on close (%s)", f->name, strerror(errno));
  46         free(f);
  47         return 0;
  48 }
  49
  50 int sha1write(struct sha1file *f, void *buf, unsigned int count)
  51 {
  52         while (count) {
  53                 unsigned offset = f->offset;
  54                 unsigned left = sizeof(f->buffer) - offset;
  55                 unsigned nr = count > left ? left : count;
  56
  57                 memcpy(f->buffer + offset, buf, nr);
  58                 count -= nr;
  59                 offset += nr;
  60                 buf += 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, 0666);
  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 struct sha1file *sha1fd(int fd, const char *name)
  99 {
 100         struct sha1file *f;
 101         unsigned len;
 102
 103         f = xmalloc(sizeof(*f));
 104
 105         len = strlen(name);
 106         if (len >= PATH_MAX)
 107                 die("you wascally wabbit, you");
 108         f->namelen = len;
 109         memcpy(f->name, name, len+1);
 110
 111         f->fd = fd;
 112         f->error = 0;
 113         f->offset = 0;
 114         SHA1_Init(&f->ctx);
 115         return f;
 116 }
 117
 118 int sha1write_compressed(struct sha1file *f, void *in, unsigned int size)
 119 {
 120         z_stream stream;
 121         unsigned long maxsize;
 122         void *out;
 123
 124         memset(&stream, 0, sizeof(stream));
 125         deflateInit(&stream, Z_DEFAULT_COMPRESSION);
 126         maxsize = deflateBound(&stream, size);
 127         out = xmalloc(maxsize);
 128
 129         /* Compress it */
 130         stream.next_in = in;
 131         stream.avail_in = size;
 132
 133         stream.next_out = out;
 134         stream.avail_out = maxsize;
 135
 136         while (deflate(&stream, Z_FINISH) == Z_OK)
 137                 /* nothing */;
 138         deflateEnd(&stream);
 139
 140         size = stream.total_out;
 141         sha1write(f, out, size);
 142         free(out);
 143         return size;
 144 }
 145
 146