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/* $XFree86: xc/programs/Xserver/hw/xfree86/ddc/edid.c,v 1.3 2000/11/03 18:46:08 eich Exp $ */
/* edid.c: retrieve EDID record from raw DDC1 data stream: data
* is contained in an array of unsigned int each unsigned int
* contains one bit if bit is 0 unsigned int has to be zero else
* unsigned int > 0
*
* Copyright 1998 by Egbert Eich <Egbert.Eich@Physik.TU-Darmstadt.DE>
*/
#include "misc.h"
#include "xf86.h"
#include "xf86_ansic.h"
#include "xf86_OSproc.h"
#include "xf86DDC.h"
#include "ddcPriv.h"
static int find_start(unsigned int *);
static unsigned char * find_header(unsigned char *);
static unsigned char * resort(unsigned char *);
unsigned char *
GetEDID_DDC1(unsigned int *s_ptr)
{
unsigned char *d_block, *d_pos;
unsigned int *s_pos, *s_end;
int s_start;
int i,j;
s_start = find_start(s_ptr);
if (s_start==-1) return NULL;
s_end = s_ptr + NUM;
s_pos = s_ptr + s_start;
d_block=xalloc(EDID1_LEN);
if (!d_block) return NULL;
d_pos = d_block;
for (i=0;i<EDID1_LEN;i++) {
for (j=0;j<8;j++) {
*d_pos <<= 1;
if (*s_pos) {
*d_pos |= 0x01;
}
s_pos++; if (s_pos == s_end) s_pos=s_ptr;
};
s_pos++; if (s_pos == s_end) s_pos=s_ptr;
d_pos++;
}
xfree(s_ptr);
if (d_block && DDC_checksum(d_block,EDID1_LEN)) return NULL;
return (resort(d_block));
}
int
DDC_checksum(unsigned char *block, int len)
{
int i, result = 0;
int not_null = 0;
for (i=0;i<len;i++) {
not_null |= block[i];
result += block[i];
}
#ifdef DEBUG
if (result & 0xFF) ErrorF("DDC checksum not correct\n");
if (!not_null) ErrorF("DDC read all Null\n");
#endif
/* catch the trivial case where all bytes are 0 */
if (!not_null) return 1;
return (result&0xFF);
}
static int
find_start(unsigned int *ptr)
{
unsigned int comp[9], test[9];
int i,j;
for (i=0;i<9;i++){
comp[i] = *(ptr++);
test[i] = 1;
}
for (i=0;i<127;i++){
for (j=0;j<9;j++){
test[j] = test[j] & !(comp[j] ^ *(ptr++));
}
}
for (i=0;i<9;i++)
if (test[i]) return (i+1);
return (-1);
}
static unsigned char *
find_header(unsigned char *block)
{
unsigned char *ptr, *head_ptr, *end;
unsigned char header[]={0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00};
ptr = block;
end = block + EDID1_LEN;
while (ptr<end) {
int i;
head_ptr = ptr;
for (i=0;i<8;i++){
if (header[i] != *(head_ptr++)) break;
if (head_ptr == end) head_ptr = block;
}
if (i==8) break;
ptr++;
}
if (ptr == end) return (NULL);
return (ptr);
}
static unsigned char *
resort(unsigned char *s_block)
{
unsigned char *d_new, *d_ptr, *d_end, *s_ptr, *s_end;
unsigned char tmp;
s_end = s_block + EDID1_LEN;
d_new = xalloc(EDID1_LEN);
if (!d_new) return NULL;
d_end = d_new + EDID1_LEN;
s_ptr = find_header(s_block);
if (!s_ptr) return NULL;
for (d_ptr=d_new;d_ptr<d_end;d_ptr++){
tmp = *(s_ptr++);
*d_ptr = tmp;
if (s_ptr == s_end) s_ptr = s_block;
}
xfree(s_block);
return (d_new);
}
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