80 lines
2.7 KiB
C
80 lines
2.7 KiB
C
/*----------------------------------------------------------------------------
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;
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; MD5 hash generator -- Paul Houle (paulhoule.com) 11/13/2017
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;
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; Non-time critical C logic. All API entry points are here.
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; See phmd5.h for documentation.
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;
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;---------------------------------------------------------------------------*/
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#include <string.h>
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#include "phmd5.h"
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// First call -- initialize pmd5 structure for use.
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void Phmd5Begin(PHMD5 *pmd5) {
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unsigned __int32 *uhash = (unsigned __int32 *) pmd5->hash;
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uhash[0] = 0x67452301; // init hash per rfc1321
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uhash[1] = 0xEFCDAB89;
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uhash[2] = 0x98BADCFE;
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uhash[3] = 0x10325476;
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pmd5->totbyt = 0; // init count of data bytes processed
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}
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// Last call -- after this, pmd5->hash holds final MD5 hash.
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void Phmd5End(PHMD5 *pmd5) {
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char pad[72]; // pad buffer (worst case is 72 bytes)
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unsigned padc; // size of needed pad (9-72 bytes)
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padc = 64 - ((unsigned) pmd5->totbyt & 63); // pad to 64-byte boundary
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if (padc < 9) padc += 64; // add a block if we need more room
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memset(pad, 0, padc); // clear entire pad area
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pad[0] = (char) 0x80; // place input stream terminator
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// place 64-bit input data bit count
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*(unsigned __int64 *) &pad[padc - 8] = pmd5->totbyt << 3;
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Phmd5Process(pmd5, pad, padc); // process the pad
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}
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// Work done here -- call for as many input blocks that need to be processed.
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// pdata points to the input data, bytecnt is pdata size (0..n bytes).
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// See phmd5.h regarding how to use this optimally.
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void Phmd5Process(PHMD5 *pmd5, char *pdata, size_t bytecnt) {
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unsigned resid = (unsigned) pmd5->totbyt;
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pmd5->totbyt += bytecnt; // update total bytes processed
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resid &= 63; // count of bytes now in pmd5->buf
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// This block handles the case of residual data in pmd5->buf.
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// After this block pmd5->buf is empty (except perhaps on exit).
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if (resid) { // if residual exists,
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unsigned cb = 64 - resid;
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if (cb > bytecnt) cb = (unsigned) bytecnt;
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memcpy(pmd5->buf + resid, pdata, cb);
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pdata += cb;
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bytecnt -= cb;
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if (resid + cb < 64) return;
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Phmd5DoBlocks(pmd5->hash, pmd5->buf, 64);
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}
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// This block processes input data in-place, if the data is dword
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// aligned and in 64-byte chunks.
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if ((unsigned) bytecnt & ~63 && ((size_t) pdata & 3) == 0) {
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Phmd5DoBlocks(pmd5->hash, pdata, bytecnt & ~63);
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pdata += bytecnt & ~63;
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bytecnt &= 63;
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}
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while (bytecnt) { // handle residual/non-aligned data
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unsigned cb = 64 > (unsigned) bytecnt ? (unsigned) bytecnt : 64;
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memcpy(pmd5->buf, pdata, cb);
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pdata += cb;
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bytecnt -= cb;
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if (cb < 64) return;
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Phmd5DoBlocks(pmd5->hash, pmd5->buf, 64);
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};
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}
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