sha2_main.c (2266B)
1 #include <stdio.h> 2 #include <string.h> 3 #include <errno.h> 4 5 #include "sha2.h" 6 7 8 #define BLOCKSIZE 4096 9 /* Ensure that BLOCKSIZE is a multiple of 64. */ 10 #if BLOCKSIZE % 64 != 0 11 /* FIXME-someday (soon?): use #error instead of this kludge. */ 12 "invalid BLOCKSIZE" 13 #endif 14 15 16 /* Compute SHA512 message digest for bytes read from STREAM. The 17 resulting message digest number will be written into the 16 bytes 18 beginning at RESBLOCK. */ 19 int 20 sha512_stream (FILE *stream, void *resblock) 21 { 22 SHA512_CTX ctx; 23 char buffer[BLOCKSIZE + 72]; 24 size_t sum; 25 26 /* Initialize the computation context. */ 27 SHA512_Init (&ctx); 28 29 /* Iterate over full file contents. */ 30 while (1) 31 { 32 /* We read the file in blocks of BLOCKSIZE bytes. One call of the 33 computation function processes the whole buffer so that with the 34 next round of the loop another block can be read. */ 35 size_t n; 36 sum = 0; 37 38 /* Read block. Take care for partial reads. */ 39 while (1) 40 { 41 n = fread (buffer + sum, 1, BLOCKSIZE - sum, stream); 42 43 sum += n; 44 45 if (sum == BLOCKSIZE) 46 break; 47 48 if (n == 0) 49 { 50 /* Check for the error flag IFF N == 0, so that we don't 51 exit the loop after a partial read due to e.g., EAGAIN 52 or EWOULDBLOCK. */ 53 if (ferror (stream)) 54 return 1; 55 goto process_partial_block; 56 } 57 58 /* We've read at least one byte, so ignore errors. But always 59 check for EOF, since feof may be true even though N > 0. 60 Otherwise, we could end up calling fread after EOF. */ 61 if (feof (stream)) 62 goto process_partial_block; 63 } 64 65 /* Process buffer with BLOCKSIZE bytes. Note that 66 BLOCKSIZE % 64 == 0 67 */ 68 SHA512_Update (&ctx, buffer, BLOCKSIZE); 69 } 70 71 process_partial_block:; 72 73 /* Process any remaining bytes. */ 74 if (sum > 0) 75 SHA512_Update (&ctx, buffer, sum); 76 77 /* Construct result in desired memory. */ 78 SHA512_Final (resblock, &ctx); 79 return 0; 80 } 81 82 int 83 main( int argc, 84 char *argv[] ) 85 { 86 unsigned char output[SHA512_DIGEST_LENGTH]; 87 int i; 88 89 if ( sha512_stream( stdin, output ) != 0 ) { 90 fprintf( stderr, "error reading stdin: errno=%i", errno ); 91 return 1; 92 } 93 94 for ( i = 0; i < sizeof( output ); i++ ) 95 printf("%02x", output[i]); 96 97 return 0; 98 } 99