// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////

//

/// \file       auto_decoder.c

/// \brief      Autodetect between .xz, .lzma (LZMA_Alone), and .lz (lzip)

//

//  Author:     Lasse Collin

//

///////////////////////////////////////////////////////////////////////////////

#include "stream_decoder.h"

#include "alone_decoder.h"

#ifdef HAVE_LZIP_DECODER

# include "lzip_decoder.h"

#endif

typedef struct {

  /// .xz Stream decoder, LZMA_Alone decoder, or lzip decoder

  lzma_next_coder next;

  uint64_t memlimit;

  uint32_t flags;

  enum {

    SEQ_INIT,

    SEQ_CODE,

    SEQ_FINISH,

  } sequence;

} lzma_auto_coder;

static lzma_ret

auto_decode(void *coder_ptr, const lzma_allocator *allocator,

    const uint8_t *restrict in, size_t *restrict in_pos,

    size_t in_size, uint8_t *restrict out,

    size_t *restrict out_pos, size_t out_size, lzma_action action)

{

  lzma_auto_coder *coder = coder_ptr;

  switch (coder->sequence) {

  case SEQ_INIT:

    if (*in_pos >= in_size)

      return LZMA_OK;

    // Update the sequence now, because we want to continue from

    // SEQ_CODE even if we return some LZMA_*_CHECK.

    coder->sequence = SEQ_CODE;

    // Detect the file format. .xz files start with 0xFD which

    // cannot be the first byte of .lzma (LZMA_Alone) format.

    // The .lz format starts with 0x4C which could be the

    // first byte of a .lzma file but luckily it would mean

    // lc/lp/pb being 4/3/1 which liblzma doesn't support because

    // lc + lp > 4. So using just 0x4C to detect .lz is OK here.

    if (in[*in_pos] == 0xFD) {

      return_if_error(lzma_stream_decoder_init(

          &coder->next, allocator,

          coder->memlimit, coder->flags));

#ifdef HAVE_LZIP_DECODER

    } else if (in[*in_pos] == 0x4C) {

      return_if_error(lzma_lzip_decoder_init(

          &coder->next, allocator,

          coder->memlimit, coder->flags));

#endif

    } else {

      return_if_error(lzma_alone_decoder_init(&coder->next,

          allocator, coder->memlimit, true));

      // If the application wants to know about missing

      // integrity check or about the check in general, we

      // need to handle it here, because LZMA_Alone decoder

      // doesn't accept any flags.

      if (coder->flags & LZMA_TELL_NO_CHECK)

        return LZMA_NO_CHECK;

      if (coder->flags & LZMA_TELL_ANY_CHECK)

        return LZMA_GET_CHECK;

    }

    FALLTHROUGH;

  case SEQ_CODE: {

    const lzma_ret ret = coder->next.code(

        coder->next.coder, allocator,

        in, in_pos, in_size,

        out, out_pos, out_size, action);

    if (ret != LZMA_STREAM_END

        || (coder->flags & LZMA_CONCATENATED) == 0)

      return ret;

    coder->sequence = SEQ_FINISH;

    FALLTHROUGH;

  }

  case SEQ_FINISH:

    // When LZMA_CONCATENATED was used and we were decoding

    // a LZMA_Alone file, we need to check that there is no

    // trailing garbage and wait for LZMA_FINISH.

    if (*in_pos < in_size)

      return LZMA_DATA_ERROR;

    return action == LZMA_FINISH ? LZMA_STREAM_END : LZMA_OK;

  default:

    assert(0);

    return LZMA_PROG_ERROR;

  }

}

static void

auto_decoder_end(void *coder_ptr, const lzma_allocator *allocator)

{

  lzma_auto_coder *coder = coder_ptr;

  lzma_next_end(&coder->next, allocator);

  lzma_free(coder, allocator);

  return;

}

static lzma_check

auto_decoder_get_check(const void *coder_ptr)

{

  const lzma_auto_coder *coder = coder_ptr;

  // It is LZMA_Alone if get_check is NULL.

  return coder->next.get_check == NULL ? LZMA_CHECK_NONE

      : coder->next.get_check(coder->next.coder);

}

static lzma_ret

auto_decoder_memconfig(void *coder_ptr, uint64_t *memusage,

    uint64_t *old_memlimit, uint64_t new_memlimit)

{

  lzma_auto_coder *coder = coder_ptr;

  lzma_ret ret;

  if (coder->next.memconfig != NULL) {

    ret = coder->next.memconfig(coder->next.coder,

        memusage, old_memlimit, new_memlimit);

    assert(*old_memlimit == coder->memlimit);

  } else {

    // No coder is configured yet. Use the base value as

    // the current memory usage.

    *memusage = LZMA_MEMUSAGE_BASE;

    *old_memlimit = coder->memlimit;

    ret = LZMA_OK;

    if (new_memlimit != 0 && new_memlimit < *memusage)

      ret = LZMA_MEMLIMIT_ERROR;

  }

  if (ret == LZMA_OK && new_memlimit != 0)

    coder->memlimit = new_memlimit;

  return ret;

}

static lzma_ret

auto_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,

    uint64_t memlimit, uint32_t flags)

{

  lzma_next_coder_init(&auto_decoder_init, next, allocator);

  if (flags & ~LZMA_SUPPORTED_FLAGS)

    return LZMA_OPTIONS_ERROR;

  lzma_auto_coder *coder = next->coder;

  if (coder == NULL) {

    coder = lzma_alloc(sizeof(lzma_auto_coder), allocator);

    if (coder == NULL)

      return LZMA_MEM_ERROR;

    next->coder = coder;

    next->code = &auto_decode;

    next->end = &auto_decoder_end;

    next->get_check = &auto_decoder_get_check;

    next->memconfig = &auto_decoder_memconfig;

    coder->next = LZMA_NEXT_CODER_INIT;

  }

  coder->memlimit = my_max(1, memlimit);

  coder->flags = flags;

  coder->sequence = SEQ_INIT;

  return LZMA_OK;

}

extern LZMA_API(lzma_ret)

lzma_auto_decoder(lzma_stream *strm, uint64_t memlimit, uint32_t flags)

{

  lzma_next_strm_init(auto_decoder_init, strm, memlimit, flags);

  strm->internal->supported_actions[LZMA_RUN] = true;

  strm->internal->supported_actions[LZMA_FINISH] = true;

  return LZMA_OK;

}