Move LZW decoder out of fx_gif

CGifLZWDecoder has been moved out into its own file, name changed to
CFX_LZWDecoder, member variable names updated, creation pattern
changed, and unit tests added.

Wrt the creation pattern, there is no longer a constructor and 2
initialization methods that need to be called. Instead all of the
initialization is done as part of the constructor. A wrapper has been
added for generating a std::unique_ptr<CFX_LZWDecoder>, so that params
can be validated.

BUG=pdfium:900,pdfium:901,pdfium:903,pdfium:904

Change-Id: Idcbe773f7fb18b08e64d5a89bfd87d4801332c53
Reviewed-on: https://pdfium-review.googlesource.com/14814
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>

1 files changed, 0 insertions, 181 deletions

diff --git a/core/fxcodec/lgif/fx_gif.cpp b/core/fxcodec/lgif/fx_gif.cpp
index 6e1c26ed12..db0744a6bb 100644
--- a/core/fxcodec/lgif/fx_gif.cpp
+++ b/core/fxcodec/lgif/fx_gif.cpp
@@ -26,184 +26,3 @@ static_assert(sizeof(GifLSD) == 7, "GifLSD should have a size of 7");
 GifImage::GifImage() {}
 
 GifImage::~GifImage() {}
-
-void CGifLZWDecoder::Input(uint8_t* src_buf, uint32_t src_size) {
-  next_in = src_buf;
-  avail_in = src_size;
-}
-
-uint32_t CGifLZWDecoder::GetAvailInput() {
-  return avail_in;
-}
-
-CGifLZWDecoder::CGifLZWDecoder(char* error_ptr)
-    : code_size(0),
-      code_size_cur(0),
-      code_clear(0),
-      code_end(0),
-      code_next(0),
-      code_first(0),
-      stack_size(0),
-      code_old(0),
-      next_in(nullptr),
-      avail_in(0),
-      bits_left(0),
-      code_store(0),
-      err_msg_ptr(error_ptr) {}
-
-CGifLZWDecoder::~CGifLZWDecoder() {}
-
-void CGifLZWDecoder::InitTable(uint8_t color_exp, uint8_t code_exp) {
-  // TODO(rharrison): Refactor all of this, so that initializing the table with
-  // bad values will kill the decompress.
-  ASSERT(code_exp <= GIF_MAX_LZW_EXP);
-  code_color_end = std::min(2 << color_exp, 1 << code_exp);
-  code_size = code_exp;
-  code_clear = 1 << code_exp;
-  code_end = code_clear + 1;
-  bits_left = 0;
-  code_store = 0;
-  next_in = nullptr;
-  avail_in = 0;
-  stack_size = 0;
-  code_first = 0;
-  ClearTable();
-}
-
-void CGifLZWDecoder::ClearTable() {
-  code_size_cur = code_size + 1;
-  code_next = code_end + 1;
-  code_old = static_cast<uint16_t>(-1);
-  memset(code_table, 0, sizeof(tag_Table) * GIF_MAX_LZW_CODE);
-  memset(stack, 0, GIF_MAX_LZW_CODE);
-  for (uint16_t i = 0; i < code_clear; i++)
-    code_table[i].suffix = static_cast<uint8_t>(i);
-}
-
-bool CGifLZWDecoder::DecodeString(uint16_t code) {
-  stack_size = 0;
-  while (code >= code_clear && code <= code_next) {
-    if (code == code_table[code].prefix || stack_size == GIF_MAX_LZW_CODE - 1)
-      return false;
-
-    stack[GIF_MAX_LZW_CODE - 1 - stack_size++] = code_table[code].suffix;
-    code = code_table[code].prefix;
-  }
-  if (code >= code_color_end)
-    return false;
-
-  stack[GIF_MAX_LZW_CODE - 1 - stack_size++] = static_cast<uint8_t>(code);
-  code_first = static_cast<uint8_t>(code);
-  return true;
-}
-
-void CGifLZWDecoder::AddCode(uint16_t prefix_code, uint8_t append_char) {
-  if (code_next == GIF_MAX_LZW_CODE)
-    return;
-
-  code_table[code_next].prefix = prefix_code;
-  code_table[code_next].suffix = append_char;
-  if (++code_next < GIF_MAX_LZW_CODE) {
-    if (code_next >> code_size_cur)
-      code_size_cur++;
-  }
-}
-
-GifDecodeStatus CGifLZWDecoder::Decode(uint8_t* des_buf, uint32_t* des_size) {
-  if (*des_size == 0)
-    return GifDecodeStatus::InsufficientDestSize;
-
-  uint32_t i = 0;
-  if (stack_size != 0) {
-    if (*des_size < stack_size) {
-      memcpy(des_buf, &stack[GIF_MAX_LZW_CODE - stack_size], *des_size);
-      stack_size -= static_cast<uint16_t>(*des_size);
-      return GifDecodeStatus::InsufficientDestSize;
-    }
-    memcpy(des_buf, &stack[GIF_MAX_LZW_CODE - stack_size], stack_size);
-    des_buf += stack_size;
-    i += stack_size;
-    stack_size = 0;
-  }
-  ASSERT(err_msg_ptr);
-  while (i <= *des_size && (avail_in > 0 || bits_left >= code_size_cur)) {
-    if (code_size_cur > GIF_MAX_LZW_EXP) {
-      strncpy(err_msg_ptr, "Code Length Out Of Range", GIF_MAX_ERROR_SIZE - 1);
-      return GifDecodeStatus::Error;
-    }
-    if (avail_in > 0) {
-      if (bits_left > 31) {
-        strncpy(err_msg_ptr, "Decode Error", GIF_MAX_ERROR_SIZE - 1);
-        return GifDecodeStatus::Error;
-      }
-      pdfium::base::CheckedNumeric<uint32_t> safe_code = *next_in++;
-      safe_code <<= bits_left;
-      safe_code |= code_store;
-      if (!safe_code.IsValid()) {
-        strncpy(err_msg_ptr, "Code Store Out Of Range", GIF_MAX_ERROR_SIZE - 1);
-        return GifDecodeStatus::Error;
-      }
-      code_store = safe_code.ValueOrDie();
-      --avail_in;
-      bits_left += 8;
-    }
-    while (bits_left >= code_size_cur) {
-      uint16_t code =
-          static_cast<uint16_t>(code_store) & ((1 << code_size_cur) - 1);
-      code_store >>= code_size_cur;
-      bits_left -= code_size_cur;
-      if (code == code_clear) {
-        ClearTable();
-        continue;
-      }
-      if (code == code_end) {
-        *des_size = i;
-        return GifDecodeStatus::Success;
-      }
-      if (code_old != static_cast<uint16_t>(-1)) {
-        if (code_next < GIF_MAX_LZW_CODE) {
-          if (code == code_next) {
-            AddCode(code_old, code_first);
-            if (!DecodeString(code)) {
-              strncpy(err_msg_ptr, "String Decoding Error",
-                      GIF_MAX_ERROR_SIZE - 1);
-              return GifDecodeStatus::Error;
-            }
-          } else if (code > code_next) {
-            strncpy(err_msg_ptr, "Decode Error, Out Of Range",
-                    GIF_MAX_ERROR_SIZE - 1);
-            return GifDecodeStatus::Error;
-          } else {
-            if (!DecodeString(code)) {
-              strncpy(err_msg_ptr, "String Decoding Error",
-                      GIF_MAX_ERROR_SIZE - 1);
-              return GifDecodeStatus::Error;
-            }
-            uint8_t append_char = stack[GIF_MAX_LZW_CODE - stack_size];
-            AddCode(code_old, append_char);
-          }
-        }
-      } else {
-        if (!DecodeString(code)) {
-          strncpy(err_msg_ptr, "String Decoding Error", GIF_MAX_ERROR_SIZE - 1);
-          return GifDecodeStatus::Error;
-        }
-      }
-      code_old = code;
-      if (i + stack_size > *des_size) {
-        memcpy(des_buf, &stack[GIF_MAX_LZW_CODE - stack_size], *des_size - i);
-        stack_size -= static_cast<uint16_t>(*des_size - i);
-        return GifDecodeStatus::InsufficientDestSize;
-      }
-      memcpy(des_buf, &stack[GIF_MAX_LZW_CODE - stack_size], stack_size);
-      des_buf += stack_size;
-      i += stack_size;
-      stack_size = 0;
-    }
-  }
-  if (avail_in == 0) {
-    *des_size = i;
-    return GifDecodeStatus::Unfinished;
-  }
-  return GifDecodeStatus::Error;
-}