/* bcjtest.c — filtro BCJ x86 standalone (E8/E9 rel32 <-> abs) p/ medir prêmio.
 * Uso: bcjtest -e in out   (rel -> abs, posição = offset global, base 0)
 *        bcjtest -d in out   (abs -> rel, inverso exato)
 * Só transforma opcode completo (5 bytes) dentro do buffer.
 */
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static void x86_fwd(uint8_t *b, size_t n){
    for(size_t i=0;i+5<=n;i++){
        if(b[i]==0xE8||b[i]==0xE9){
            uint32_t rel=b[i+1]|((uint32_t)b[i+2]<<8)|((uint32_t)b[i+3]<<16)|((uint32_t)b[i+4]<<24);
            uint32_t abs=(uint32_t)(i+rel+5);
            b[i+1]=(uint8_t)abs; b[i+2]=(uint8_t)(abs>>8); b[i+3]=(uint8_t)(abs>>16); b[i+4]=(uint8_t)(abs>>24);
            i+=4;
        }
    }
}
static void x86_inv(uint8_t *b, size_t n){
    for(size_t i=0;i+5<=n;i++){
        if(b[i]==0xE8||b[i]==0xE9){
            uint32_t abs=b[i+1]|((uint32_t)b[i+2]<<8)|((uint32_t)b[i+3]<<16)|((uint32_t)b[i+4]<<24);
            uint32_t rel=abs-(uint32_t)(i+5);
            b[i+1]=(uint8_t)rel; b[i+2]=(uint8_t)(rel>>8); b[i+3]=(uint8_t)(rel>>16); b[i+4]=(uint8_t)(rel>>24);
            i+=4;
        }
    }
}
static uint8_t *slurp(const char *p,size_t *n){
    FILE *f=fopen(p,"rb"); if(!f) return NULL;
    fseek(f,0,SEEK_END); long nb=ftell(f); fseek(f,0,SEEK_SET);
    if(nb<=0){ fclose(f); return NULL; }
    uint8_t *b=malloc(nb); if(fread(b,1,nb,f)!=(size_t)nb){ fclose(f); free(b); return NULL; }
    fclose(f); *n=nb; return b;
}
int main(int argc,char**argv){
    if(argc!=4){ printf("Uso: %s -e|-d entrada saida\n",argv[0]); return 1; }
    size_t n=0; uint8_t *b=slurp(argv[2],&n); if(!b){ printf("open fail\n"); return 1; }
    /* conta E8/E9 p/ diagnóstico */
    size_t cnt=0; for(size_t i=0;i+5<=n;i++) if(b[i]==0xE8||b[i]==0xE9){ cnt++; i+=4; }
    if(strcmp(argv[1],"-e")==0) x86_fwd(b,n); else x86_inv(b,n);
    FILE *f=fopen(argv[3],"wb"); if(!f){ printf("create fail\n"); free(b); return 1; }
    fwrite(b,1,n,f); fclose(f); free(b);
    printf("BCJ %s: %zu bytes, %zu opcodes E8/E9\n",argv[1],n,cnt);
    return 0;
}