int dcnids_read_header(int fd, int skipcount,
struct nids_header_st *nheader){
int n;
int status;
unsigned char *b;
int b_size;
char skipbuffer[4096];
size_t skipbuffer_size = 4096;
memset(nheader, 0, sizeof(struct nids_header_st));
nheader->buffer_size = WMOAWIPS_HEADER_SIZE + NIDS_HEADER_SIZE;
b = &nheader->buffer[0];
b_size = nheader->buffer_size;
if(skipcount != 0){
status = read_skip_count(fd, skipcount, skipbuffer, skipbuffer_size);
if(status != 0)
return(status);
}
/*
* If the file has a gempak header, skip it.
*/
n = read(fd, b, 1);
if(n != 1)
return(-1);
if(isalnum(*b) == 0){
/*
* Assume it is a gempak header
*/
status = read_skip_count(fd, GMPK_HEADER_SIZE - 1,
skipbuffer, skipbuffer_size);
if(status != 0)
return(status);
}else{
/*
* Read what is left of the real header.
*/
++b;
--b_size;
}
n = read(fd, b, b_size);
if(n == -1)
return(-1);
else if(n < b_size)
return(1);
return(0);
}
static int read_code_table(LHANewDecoder *decoder)
{
int i, j, n, skip_count, code;
uint8_t code_lengths[NUM_CODES];
// How many codes?
n = read_bits(&decoder->bit_stream_reader, 9);
if (n < 0) {
return 0;
}
// n=0 implies a single code of zero length; all inputs
// decode to the same code.
if (n == 0) {
code = read_bits(&decoder->bit_stream_reader, 9);
if (code < 0) {
return 0;
}
set_tree_single(decoder->code_tree, code);
return 1;
}
if (n > NUM_CODES) {
n = NUM_CODES;
}
// Read the length of each code.
// The lengths are encoded using the temp-table previously read;
// offset_tree is reused temporarily to hold it.
i = 0;
while (i < n) {
code = read_from_tree(&decoder->bit_stream_reader,
decoder->offset_tree);
if (code < 0) {
return 0;
}
// The code that was read can have different meanings.
// If in the range 0-2, it indicates that a number of
// codes are unused and should be skipped over.
// Values greater than two represent a frequency count.
if (code <= 2) {
skip_count = read_skip_count(decoder, code);
if (skip_count < 0) {
return 0;
}
for (j = 0; j < skip_count && i < n; ++j) {
code_lengths[i] = 0;
++i;
}
} else {
code_lengths[i] = code - 2;
++i;
}
}
build_tree(decoder->code_tree, NUM_CODES * 2, code_lengths, n);
return 1;
}
