/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/intrin/bits.h"
#include "libc/log/libfatal.internal.h"
#include "libc/macros.internal.h"
#include "libc/str/str.h"

#define TRIES 8

/**
 * Returns offset of binary embedded inside binary.
 *
 * This can be used to load zip assets from an executable that hasn't
 * gone through the `objcopy -S -O binary` step. We make the assumption
 * that an x86_64-pc-linux-gnu toolchain is being used. This routine
 * would need to be changed to accommodate binaries built locally on
 * Apple, FreeBSD, etc.
 *
 * @param p needs to be page aligned
 * @param n is byte length of p
 * @return base address of image or NULL if not found
 */
uint8_t *FindEmbeddedApe(const uint8_t *p, size_t n) {
  size_t i;
  uint64_t w;
  n = MIN(n, TRIES * PAGESIZE);
  for (i = 0; i + 8 <= n; i += PAGESIZE) {
    w = READ64LE(p + i);
    if (w == READ64LE("MZqFpD='") || w == READ64LE("\177ELF\2\1\1\11")) {
      return (/*unconst*/ uint8_t *)(p + i);
    }
  }
  return 0;
}
