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bit_array.cpp
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bit_array.cpp
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#include <limits.h>
#include <string.h>
#include <stddef.h>
#include "bit_array.hpp"
#define PREPARE_FIRST_COPY() \
do { \
if (src_len >= (CHAR_BIT - dst_offset_modulo)) { \
*dst &= reverse_mask[dst_offset_modulo]; \
src_len -= CHAR_BIT - dst_offset_modulo; \
} else { \
*dst &= reverse_mask[dst_offset_modulo] \
| reverse_mask_xor[dst_offset_modulo + src_len + 1];\
c &= reverse_mask[dst_offset_modulo + src_len ];\
src_len = 0; \
} } while (0)
void
bitarray_copy(const unsigned char *src_org, int src_offset, int src_len,
unsigned char *dst_org, int dst_offset)
{
/*static const unsigned char mask[] =
{ 0x55, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff };
static const unsigned char mask_xor[] =
{ 0x55, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00 };*/
static const unsigned char reverse_mask[] =
{ 0x55, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe, 0xff };
static const unsigned char reverse_mask_xor[] =
{ 0xff, 0x7f, 0x3f, 0x1f, 0x0f, 0x07, 0x03, 0x01, 0x00 };
if (src_len) {
const unsigned char *src;
unsigned char *dst;
int src_offset_modulo,
dst_offset_modulo;
src = src_org + (src_offset / CHAR_BIT);
dst = dst_org + (dst_offset / CHAR_BIT);
src_offset_modulo = src_offset % CHAR_BIT;
dst_offset_modulo = dst_offset % CHAR_BIT;
if (src_offset_modulo == dst_offset_modulo) {
int byte_len;
int src_len_modulo;
if (src_offset_modulo) {
unsigned char c;
c = reverse_mask_xor[dst_offset_modulo] & *src++;
PREPARE_FIRST_COPY();
*dst++ |= c;
}
byte_len = src_len / CHAR_BIT;
src_len_modulo = src_len % CHAR_BIT;
if (byte_len) {
memcpy(dst, src, byte_len);
src += byte_len;
dst += byte_len;
}
if (src_len_modulo) {
*dst &= reverse_mask_xor[src_len_modulo];
*dst |= reverse_mask[src_len_modulo] & *src;
}
} else {
int bit_diff_ls,
bit_diff_rs;
int byte_len;
int src_len_modulo;
unsigned char c;
/*
* Begin: Line things up on destination.
*/
if (src_offset_modulo > dst_offset_modulo) {
bit_diff_ls = src_offset_modulo - dst_offset_modulo;
bit_diff_rs = CHAR_BIT - bit_diff_ls;
c = *src++ << bit_diff_ls;
c |= *src >> bit_diff_rs;
c &= reverse_mask_xor[dst_offset_modulo];
} else {
bit_diff_rs = dst_offset_modulo - src_offset_modulo;
bit_diff_ls = CHAR_BIT - bit_diff_rs;
c = *src >> bit_diff_rs &
reverse_mask_xor[dst_offset_modulo];
}
PREPARE_FIRST_COPY();
*dst++ |= c;
/*
* Middle: copy with only shifting the source.
*/
byte_len = src_len / CHAR_BIT;
while (--byte_len >= 0) {
c = *src++ << bit_diff_ls;
c |= *src >> bit_diff_rs;
*dst++ = c;
}
/*
* End: copy the remaing bits;
*/
src_len_modulo = src_len % CHAR_BIT;
if (src_len_modulo) {
c = *src++ << bit_diff_ls;
c |= *src >> bit_diff_rs;
c &= reverse_mask[src_len_modulo];
*dst &= reverse_mask_xor[src_len_modulo];
*dst |= c;
}
}
}
}