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#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "crypto_buffer.h"
/* after this s->e_ptr and s->e_end are updated */
static int firstread(crypto_buffer *s)
{
register u8 *ptr1, *ptr2, *buffer;
register u32 size;
u32 r, i;
/* look for the 0x5a block */
buffer = s->e_buffer;
size = s->block_size;
for(;;){
ptr1 = ptr2 = buffer;
r = s->op(s->fd, buffer, s->e_len);
if (r == 0) return 0; /* end of file */
if (r == -1){
if (errno == EINTR) continue; /* reread */
return r; /* read error */
}
if (r <= (size << 1)) return -1; /* no data */
i = r;
do{
i -= (ptr1-ptr2);
if (i==0) { ptr2 = NULL; break; } /* force reread */
ptr2 = memchr(ptr1, 0x5a, i);
if (ptr2 == NULL) break; /* reread */
ptr1 = ptr2;
for(;;) { if(*ptr1++!=0x5a) break; }
}while(ptr1-ptr2 < size);
if (ptr2 != NULL) break;
}
/* now ptr2 points to the 0x5a block */
ptr2 += size;
/* decrypt info */
s->cipher(&s->ctx,buffer, ptr2);
s->data_st.bytes = ((struct info *)buffer)->bytes;
s->data_st.strlen = ((struct info *)buffer)->strlen;
s->e_ptr = ptr2 + size;
r -= (size << 1);
i = s->e_ptr - (u8*)s->e_data - size;
if(i>0){
memmove(s->e_ptr-i, s->e_ptr, r-i);
s->e_ptr -= i;
if(s->op(s->fd, s->e_ptr+r-i, i)<=0) return r; /* really bad */
}
s->e_end = s->e_ptr + r;
return r;
}
/* after this s->e_ptr and s->e_end are updated */
static int oneread(crypto_buffer *s)
{
int r;
for (;;) {
r = s->op(s->fd,s->e_buffer,s->e_len);
if (r == -1) if (errno == EINTR) continue;
s->e_ptr = s->e_buffer;
s->e_end = s->e_ptr + r;
return r;
}
}
/* after this s->e_ptr is updated */
static int eatinfo(crypto_buffer *s, u8* start)
{
register u32 size;
register u8* buffer;
register u8* current;
int ret;
/* be really carefull */
current = start;
size = s->block_size;
buffer = s->e_buffer;
if(current == s->e_end){
ret = oneread(s);
if(ret<=0) return ret; /* error */
current = buffer;
}
/* TODO ?? verify that it's a magic block */
current += size; /* jump over 0x5a block */
if(current == s->e_end){
ret = oneread(s);
if(ret<=0) return ret; /* error */
current = buffer;
}
s->cipher(&s->ctx,buffer,current);
s->data_st.bytes = ((struct info *)buffer)->bytes;
s->data_st.strlen = ((struct info *)buffer)->strlen;
current += size; /* jump over info */
if(current == s->e_end){
ret = oneread(s);
if(ret<=0) return ret; /* error */
current = buffer;
}
s->e_ptr = current;
return 1;
}
/* afer this s->c_ptr is updated */
static int getthis(crypto_buffer *s, u8 *buf, u32 len)
{
int available;
available = s->c_end - s->c_ptr;
if (len > available) len = available;
memcpy(buf, s->c_ptr, len);
s->c_ptr += len;
return len;
}
int crypto_buffer_get(crypto_buffer *s, u8 *buf, u32 len)
{
register u32 need;
register u32 size;
register u8* e_end;
register u8* e_ptr;
int r, ret;
r = 0;
need = len;
size = s->block_size;
if(s->e_ptr == s->e_buffer){
ret = firstread(s);
if(ret <=0) return ret;
}
if (s->c_ptr != s->c_buffer){ /* TODO maybe else if */
r = getthis(s,buf,need);
if (r == need )return r;
need -= r;
buf += r;
}
/* now s->c_buffer is empty */
e_end = s->e_end;
e_ptr = s->e_ptr;
while(need){
if(e_ptr == e_end){
/* buffer empty */
ret = oneread(s);
if(ret < 0) return ret;
if(ret == 0) return r;
e_ptr = s->e_ptr;
e_end = s->e_end;
}
if(s->data_st.bytes == 0) {
/* end of raw encrypted data */
ret = eatinfo(s,e_ptr);
if(ret < 0) return ret;
if(ret == 0) return r;
e_ptr = s->e_ptr;
}
s->cipher(&s->ctx, s->c_buffer, e_ptr);
s->data_st.bytes -= size;
e_ptr += size;
/* now c_buffer is full */
if(s->data_st.strlen < size){
/* non fully used block */
s->c_ptr = s->c_end - s->data_st.strlen;
memmove(s->c_ptr, s->c_buffer, s->data_st.strlen);
} else {
s->data_st.strlen -= size;
s->c_ptr = s->c_buffer;
}
ret = getthis(s,buf,need);
need -= ret;
buf += ret;
r+= ret;
}
s->e_ptr = e_ptr;
return r;
}
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