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/*
* cifra - embedded cryptography library
* Written in 2014 by Joseph Birr-Pixton <jpixton@gmail.com>
*
* To the extent possible under law, the author(s) have dedicated all
* copyright and related and neighboring rights to this software to the
* public domain worldwide. This software is distributed without any
* warranty.
*
* You should have received a copy of the CC0 Public Domain Dedication
* along with this software. If not, see
* <http://creativecommons.org/publicdomain/zero/1.0/>.
*/
#include <bitops.h>
#include <blockwise.h>
#include <handy.h>
#include <tassert.h>
#include <string.h>
void cf_blockwise_accumulate(uint8_t *partial, size_t *npartial, size_t nblock,
const void *inp, size_t nbytes,
cf_blockwise_in_fn process,
void *ctx)
{
cf_blockwise_accumulate_final(partial, npartial, nblock,
inp, nbytes,
process, process, ctx);
}
void cf_blockwise_accumulate_final(uint8_t *partial, size_t *npartial, size_t nblock,
const void *inp, size_t nbytes,
cf_blockwise_in_fn process,
cf_blockwise_in_fn process_final,
void *ctx)
{
const uint8_t *bufin = inp;
assert(partial && *npartial < nblock);
assert(inp || !nbytes);
assert(process && ctx);
/* If we have partial data, copy in to buffer. */
if (*npartial && nbytes)
{
size_t space = nblock - *npartial;
size_t taken = MIN(space, nbytes);
memcpy(partial + *npartial, bufin, taken);
bufin += taken;
nbytes -= taken;
*npartial += taken;
/* If that gives us a full block, process it. */
if (*npartial == nblock)
{
if (nbytes == 0)
process_final(ctx, partial);
else
process(ctx, partial);
*npartial = 0;
}
}
/* now nbytes < nblock or *npartial == 0. */
/* If we have a full block of data, process it directly. */
while (nbytes >= nblock)
{
/* Partial buffer must be empty, or we're ignoring extant data */
assert(*npartial == 0);
if (nbytes == nblock)
process_final(ctx, bufin);
else
process(ctx, bufin);
bufin += nblock;
nbytes -= nblock;
}
/* Finally, if we have remaining data, buffer it. */
while (nbytes)
{
size_t space = nblock - *npartial;
size_t taken = MIN(space, nbytes);
memcpy(partial + *npartial, bufin, taken);
bufin += taken;
nbytes -= taken;
*npartial += taken;
/* If we started with *npartial, we must have copied it
* in first. */
assert(*npartial < nblock);
}
}
void cf_blockwise_xor(uint8_t *partial, size_t *npartial, size_t nblock,
const void *inp, void *outp, size_t nbytes,
cf_blockwise_out_fn process, void *ctx)
{
const uint8_t *inb = inp;
uint8_t *outb = outp;
assert(partial && *npartial < nblock);
assert(inp || !nbytes);
assert(process && ctx);
while (nbytes)
{
/* If we're out of material, and need more, produce a block. */
if (*npartial == 0)
{
process(ctx, partial);
*npartial = nblock;
}
size_t offset = nblock - *npartial;
size_t taken = MIN(*npartial, nbytes);
xor_bb(outb, inb, partial + offset, taken);
*npartial -= taken;
nbytes -= taken;
outb += taken;
inb += taken;
}
}
void cf_blockwise_acc_byte(uint8_t *partial, size_t *npartial,
size_t nblock,
uint8_t byte, size_t nbytes,
cf_blockwise_in_fn process,
void *ctx)
{
/* only memset the whole of the block once */
int filled = 0;
while (nbytes)
{
size_t start = *npartial;
size_t count = MIN(nbytes, nblock - start);
if (!filled)
memset(partial + start, byte, count);
if (start == 0 && count == nblock)
filled = 1;
if (start + count == nblock)
{
process(ctx, partial);
*npartial = 0;
} else {
*npartial += count;
}
nbytes -= count;
}
}
void cf_blockwise_acc_pad(uint8_t *partial, size_t *npartial,
size_t nblock,
uint8_t fbyte, uint8_t mbyte, uint8_t lbyte,
size_t nbytes,
cf_blockwise_in_fn process,
void *ctx)
{
switch (nbytes)
{
case 0: break;
case 1: fbyte ^= lbyte;
cf_blockwise_accumulate(partial, npartial, nblock, &fbyte, 1, process, ctx);
break;
case 2:
cf_blockwise_accumulate(partial, npartial, nblock, &fbyte, 1, process, ctx);
cf_blockwise_accumulate(partial, npartial, nblock, &lbyte, 1, process, ctx);
break;
default:
cf_blockwise_accumulate(partial, npartial, nblock, &fbyte, 1, process, ctx);
/* If the middle and last bytes differ, then process the last byte separately.
* Otherwise, just extend the middle block size. */
if (lbyte != mbyte)
{
cf_blockwise_acc_byte(partial, npartial, nblock, mbyte, nbytes - 2, process, ctx);
cf_blockwise_accumulate(partial, npartial, nblock, &lbyte, 1, process, ctx);
} else {
cf_blockwise_acc_byte(partial, npartial, nblock, mbyte, nbytes - 1, process, ctx);
}
break;
}
}
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