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added from dvdnav's dvdread getbits() code to be used in forthcoming patch to read correctly NAV data

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git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@24101 b3059339-0415-0410-9bf9-f77b7e298cf2
This commit is contained in:
nicodvb 2007-08-19 20:53:43 +00:00
parent d130a78de5
commit 0f6e7bd095
1 changed files with 70 additions and 0 deletions
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70
dvdread/nav_read.c
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@ -32,6 +32,76 @@
#include "nav_read.h"
#include "dvdread_internal.h"
typedef struct {
uint8_t *start;
uint32_t byte_position;
uint32_t bit_position;
uint8_t byte;
} getbits_state_t;
static int getbits_init(getbits_state_t *state, uint8_t *start) {
if ((state == NULL) || (start == NULL)) return 0;
state->start = start;
state->bit_position = 0;
state->byte_position = 0;
state->byte = start[0];
return 1;
}
/* Non-optimized getbits. */
/* This can easily be optimized for particular platforms. */
static uint32_t getbits(getbits_state_t *state, uint32_t number_of_bits) {
uint32_t result=0;
uint8_t byte=0;
if (number_of_bits > 32) {
printf("Number of bits > 32 in getbits\n");
abort();
}
if ((state->bit_position) > 0) { /* Last getbits left us in the middle of a byte. */
if (number_of_bits > (8-state->bit_position)) { /* this getbits will span 2 or more bytes. */
byte = state->byte;
byte = byte >> (state->bit_position);
result = byte;
number_of_bits -= (8-state->bit_position);
state->bit_position = 0;
state->byte_position++;
state->byte = state->start[state->byte_position];
} else {
byte=state->byte;
state->byte = state->byte << number_of_bits;
byte = byte >> (8 - number_of_bits);
result = byte;
state->bit_position += number_of_bits; /* Here it is impossible for bit_position > 8 */
if (state->bit_position == 8) {
state->bit_position = 0;
state->byte_position++;
state->byte = state->start[state->byte_position];
}
number_of_bits = 0;
}
}
if ((state->bit_position) == 0) {
while (number_of_bits > 7) {
result = (result << 8) + state->byte;
state->byte_position++;
state->byte = state->start[state->byte_position];
number_of_bits -= 8;
}
if (number_of_bits > 0) { /* number_of_bits < 8 */
byte = state->byte;
state->byte = state->byte << number_of_bits;
state->bit_position += number_of_bits; /* Here it is impossible for bit_position > 7 */
byte = byte >> (8 - number_of_bits);
result = (result << number_of_bits) + byte;
number_of_bits = 0;
}
}
return result;
}
void navRead_PCI(pci_t *pci, unsigned char *buffer) {
int i, j;