Merge to XFA: Cleanup some fx_codec_fax.cpp code.

R=tsepez@chromium.org
TBR=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1367633005 .

(cherry picked from commit 39cd934a4705f69c30e1bbf13eab347f66999020)

Review URL: https://codereview.chromium.org/1370273002 .

3 files changed, 351 insertions, 346 deletions

diff --git a/core/src/fxcodec/codec/fx_codec_fax.cpp b/core/src/fxcodec/codec/fx_codec_fax.cpp
index 394e22b013..ff9d45d256 100644
--- a/core/src/fxcodec/codec/fx_codec_fax.cpp
+++ b/core/src/fxcodec/codec/fx_codec_fax.cpp
@@ -6,6 +6,9 @@
 
 #include "../../../include/fxcodec/fx_codec.h"
 #include "codec_int.h"
+
+namespace {
+
 const uint8_t OneLeadPos[256] = {
     8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
@@ -33,7 +36,7 @@ const uint8_t ZeroLeadPos[256] = {
     4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 7, 8,
 };
 
-int _FindBit(const uint8_t* data_buf, int max_pos, int start_pos, int bit) {
+int FindBit(const uint8_t* data_buf, int max_pos, int start_pos, int bit) {
   if (start_pos >= max_pos) {
     return max_pos;
   }
@@ -68,33 +71,32 @@ int _FindBit(const uint8_t* data_buf, int max_pos, int start_pos, int bit) {
   }
   return pos;
 }
-void _FaxG4FindB1B2(const uint8_t* ref_buf,
-                    int columns,
-                    int a0,
-                    FX_BOOL a0color,
-                    int& b1,
-                    int& b2) {
-  if (a0color) {
-    a0color = 1;
-  }
+
+void FaxG4FindB1B2(const uint8_t* ref_buf,
+                   int columns,
+                   int a0,
+                   bool a0color,
+                   int& b1,
+                   int& b2) {
   uint8_t first_bit =
       (a0 < 0) ? 1 : ((ref_buf[a0 / 8] & (1 << (7 - a0 % 8))) != 0);
-  b1 = _FindBit(ref_buf, columns, a0 + 1, !first_bit);
+  b1 = FindBit(ref_buf, columns, a0 + 1, !first_bit);
   if (b1 >= columns) {
     b1 = b2 = columns;
     return;
   }
   if (first_bit == !a0color) {
-    b1 = _FindBit(ref_buf, columns, b1 + 1, first_bit);
+    b1 = FindBit(ref_buf, columns, b1 + 1, first_bit);
     first_bit = !first_bit;
   }
   if (b1 >= columns) {
     b1 = b2 = columns;
     return;
   }
-  b2 = _FindBit(ref_buf, columns, b1 + 1, first_bit);
+  b2 = FindBit(ref_buf, columns, b1 + 1, first_bit);
 }
-void _FaxFillBits(uint8_t* dest_buf, int columns, int startpos, int endpos) {
+
+void FaxFillBits(uint8_t* dest_buf, int columns, int startpos, int endpos) {
   if (startpos < 0) {
     startpos = 0;
   }
@@ -126,6 +128,7 @@ void _FaxFillBits(uint8_t* dest_buf, int columns, int startpos, int endpos) {
     FXSYS_memset(dest_buf + first_byte + 1, 0, last_byte - first_byte - 1);
   }
 }
+
 #define NEXTBIT                                  \
   src_buf[bitpos / 8] & (1 << (7 - bitpos % 8)); \
   bitpos++;
@@ -134,7 +137,8 @@ void _FaxFillBits(uint8_t* dest_buf, int columns, int startpos, int endpos) {
   if (bit)                \
     code++;
 #define GETBIT(bitpos) src_buf[bitpos / 8] & (1 << (7 - bitpos % 8))
-static const uint8_t FaxBlackRunIns[] = {
+
+const uint8_t FaxBlackRunIns[] = {
     0,          2,          0x02,       3,          0,          0x03,
     2,          0,          2,          0x02,       1,          0,
     0x03,       4,          0,          2,          0x02,       6,
@@ -190,7 +194,8 @@ static const uint8_t FaxBlackRunIns[] = {
     960 / 256,  0x74,       1024 % 256, 1024 / 256, 0x75,       1088 % 256,
     1088 / 256, 0x76,       1152 % 256, 1152 / 256, 0x77,       1216 % 256,
     1216 / 256, 0xff};
-static const uint8_t FaxWhiteRunIns[] = {
+
+const uint8_t FaxWhiteRunIns[] = {
     0,          0,          0,          6,          0x07,       2,
     0,          0x08,       3,          0,          0x0B,       4,
     0,          0x0C,       5,          0,          0x0E,       6,
@@ -247,10 +252,11 @@ static const uint8_t FaxWhiteRunIns[] = {
     0x1e,       2496 % 256, 2496 / 256, 0x1f,       2560 % 256, 2560 / 256,
     0xff,
 };
-int _FaxGetRun(const uint8_t* ins_array,
-               const uint8_t* src_buf,
-               int& bitpos,
-               int bitsize) {
+
+int FaxGetRun(const uint8_t* ins_array,
+              const uint8_t* src_buf,
+              int& bitpos,
+              int bitsize) {
   FX_DWORD code = 0;
   int ins_off = 0;
   while (1) {
@@ -274,188 +280,137 @@ int _FaxGetRun(const uint8_t* ins_array,
     }
   }
 }
-FX_BOOL _FaxG4GetRow(const uint8_t* src_buf,
-                     int bitsize,
-                     int& bitpos,
-                     uint8_t* dest_buf,
-                     const uint8_t* ref_buf,
-                     int columns) {
-  int a0 = -1, a0color = 1;
-  while (1) {
-    if (bitpos >= bitsize) {
-      return FALSE;
-    }
-    int a1, a2, b1, b2;
-    _FaxG4FindB1B2(ref_buf, columns, a0, a0color, b1, b2);
-    FX_BOOL bit = NEXTBIT;
-    int v_delta = 0;
-    if (bit) {
-    } else {
-      if (bitpos >= bitsize) {
-        return FALSE;
-      }
-      FX_BOOL bit1 = NEXTBIT;
-      if (bitpos >= bitsize) {
-        return FALSE;
-      }
-      FX_BOOL bit2 = NEXTBIT;
-      if (bit1 && bit2) {
-        v_delta = 1;
-      } else if (bit1) {
-        v_delta = -1;
-      } else if (bit2) {
-        int run_len1 = 0;
-        while (1) {
-          int run = _FaxGetRun(a0color ? FaxWhiteRunIns : FaxBlackRunIns,
-                               src_buf, bitpos, bitsize);
-          run_len1 += run;
-          if (run < 64) {
-            break;
-          }
-        }
-        if (a0 < 0) {
-          run_len1++;
-        }
-        a1 = a0 + run_len1;
-        if (!a0color) {
-          _FaxFillBits(dest_buf, columns, a0, a1);
-        }
-        int run_len2 = 0;
-        while (1) {
-          int run = _FaxGetRun(a0color ? FaxBlackRunIns : FaxWhiteRunIns,
-                               src_buf, bitpos, bitsize);
-          run_len2 += run;
-          if (run < 64) {
-            break;
-          }
-        }
-        a2 = a1 + run_len2;
-        if (a0color) {
-          _FaxFillBits(dest_buf, columns, a1, a2);
-        }
-        a0 = a2;
-        if (a0 < columns) {
-          continue;
-        }
-        return TRUE;
-      } else {
-        if (bitpos >= bitsize) {
-          return FALSE;
-        }
-        bit = NEXTBIT;
-        if (bit) {
-          if (!a0color) {
-            _FaxFillBits(dest_buf, columns, a0, b2);
-          }
-          if (b2 >= columns) {
-            return TRUE;
-          }
-          a0 = b2;
-          continue;
-        } else {
-          if (bitpos >= bitsize) {
-            return FALSE;
-          }
-          FX_BOOL bit1 = NEXTBIT;
-          if (bitpos >= bitsize) {
-            return FALSE;
-          }
-          FX_BOOL bit2 = NEXTBIT;
-          if (bit1 && bit2) {
-            v_delta = 2;
-          } else if (bit1) {
-            v_delta = -2;
-          } else if (bit2) {
-            if (bitpos >= bitsize) {
-              return FALSE;
-            }
-            bit = NEXTBIT;
-            if (bit) {
-              v_delta = 3;
-            } else {
-              v_delta = -3;
-            }
-          } else {
-            if (bitpos >= bitsize) {
-              return FALSE;
-            }
-            bit = NEXTBIT;
-            if (bit) {
-              bitpos += 3;
-              continue;
-            } else {
-              bitpos += 5;
-              return TRUE;
-            }
-          }
-        }
-      }
-    }
-    a1 = b1 + v_delta;
-    if (!a0color) {
-      _FaxFillBits(dest_buf, columns, a0, a1);
-    }
-    if (a1 >= columns) {
-      return TRUE;
+
+const uint8_t BlackRunTerminator[128] = {
+    0x37, 10, 0x02, 3,  0x03, 2,  0x02, 2,  0x03, 3,  0x03, 4,  0x02, 4,
+    0x03, 5,  0x05, 6,  0x04, 6,  0x04, 7,  0x05, 7,  0x07, 7,  0x04, 8,
+    0x07, 8,  0x18, 9,  0x17, 10, 0x18, 10, 0x08, 10, 0x67, 11, 0x68, 11,
+    0x6c, 11, 0x37, 11, 0x28, 11, 0x17, 11, 0x18, 11, 0xca, 12, 0xcb, 12,
+    0xcc, 12, 0xcd, 12, 0x68, 12, 0x69, 12, 0x6a, 12, 0x6b, 12, 0xd2, 12,
+    0xd3, 12, 0xd4, 12, 0xd5, 12, 0xd6, 12, 0xd7, 12, 0x6c, 12, 0x6d, 12,
+    0xda, 12, 0xdb, 12, 0x54, 12, 0x55, 12, 0x56, 12, 0x57, 12, 0x64, 12,
+    0x65, 12, 0x52, 12, 0x53, 12, 0x24, 12, 0x37, 12, 0x38, 12, 0x27, 12,
+    0x28, 12, 0x58, 12, 0x59, 12, 0x2b, 12, 0x2c, 12, 0x5a, 12, 0x66, 12,
+    0x67, 12,
+};
+
+const uint8_t BlackRunMarkup[80] = {
+    0x0f, 10, 0xc8, 12, 0xc9, 12, 0x5b, 12, 0x33, 12, 0x34, 12, 0x35, 12,
+    0x6c, 13, 0x6d, 13, 0x4a, 13, 0x4b, 13, 0x4c, 13, 0x4d, 13, 0x72, 13,
+    0x73, 13, 0x74, 13, 0x75, 13, 0x76, 13, 0x77, 13, 0x52, 13, 0x53, 13,
+    0x54, 13, 0x55, 13, 0x5a, 13, 0x5b, 13, 0x64, 13, 0x65, 13, 0x08, 11,
+    0x0c, 11, 0x0d, 11, 0x12, 12, 0x13, 12, 0x14, 12, 0x15, 12, 0x16, 12,
+    0x17, 12, 0x1c, 12, 0x1d, 12, 0x1e, 12, 0x1f, 12,
+};
+
+const uint8_t WhiteRunTerminator[128] = {
+    0x35, 8, 0x07, 6, 0x07, 4, 0x08, 4, 0x0B, 4, 0x0C, 4, 0x0E, 4, 0x0F, 4,
+    0x13, 5, 0x14, 5, 0x07, 5, 0x08, 5, 0x08, 6, 0x03, 6, 0x34, 6, 0x35, 6,
+    0x2a, 6, 0x2B, 6, 0x27, 7, 0x0c, 7, 0x08, 7, 0x17, 7, 0x03, 7, 0x04, 7,
+    0x28, 7, 0x2B, 7, 0x13, 7, 0x24, 7, 0x18, 7, 0x02, 8, 0x03, 8, 0x1a, 8,
+    0x1b, 8, 0x12, 8, 0x13, 8, 0x14, 8, 0x15, 8, 0x16, 8, 0x17, 8, 0x28, 8,
+    0x29, 8, 0x2a, 8, 0x2b, 8, 0x2c, 8, 0x2d, 8, 0x04, 8, 0x05, 8, 0x0a, 8,
+    0x0b, 8, 0x52, 8, 0x53, 8, 0x54, 8, 0x55, 8, 0x24, 8, 0x25, 8, 0x58, 8,
+    0x59, 8, 0x5a, 8, 0x5b, 8, 0x4a, 8, 0x4b, 8, 0x32, 8, 0x33, 8, 0x34, 8,
+};
+
+const uint8_t WhiteRunMarkup[80] = {
+    0x1b, 5,  0x12, 5,  0x17, 6,  0x37, 7,  0x36, 8,  0x37, 8,  0x64, 8,
+    0x65, 8,  0x68, 8,  0x67, 8,  0xcc, 9,  0xcd, 9,  0xd2, 9,  0xd3, 9,
+    0xd4, 9,  0xd5, 9,  0xd6, 9,  0xd7, 9,  0xd8, 9,  0xd9, 9,  0xda, 9,
+    0xdb, 9,  0x98, 9,  0x99, 9,  0x9a, 9,  0x18, 6,  0x9b, 9,  0x08, 11,
+    0x0c, 11, 0x0d, 11, 0x12, 12, 0x13, 12, 0x14, 12, 0x15, 12, 0x16, 12,
+    0x17, 12, 0x1c, 12, 0x1d, 12, 0x1e, 12, 0x1f, 12,
+};
+
+void AddBitStream(uint8_t* dest_buf, int& dest_bitpos, int data, int bitlen) {
+  for (int i = bitlen - 1; i >= 0; i--) {
+    if (data & (1 << i)) {
+      dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
     }
-    a0 = a1;
-    a0color = !a0color;
+    dest_bitpos++;
   }
 }
-FX_BOOL _FaxSkipEOL(const uint8_t* src_buf, int bitsize, int& bitpos) {
-  int startbit = bitpos;
-  while (bitpos < bitsize) {
-    int bit = NEXTBIT;
-    if (bit) {
-      if (bitpos - startbit <= 11) {
-        bitpos = startbit;
-      }
-      return TRUE;
-    }
+
+void FaxEncodeRun(uint8_t* dest_buf, int& dest_bitpos, int run, bool bWhite) {
+  while (run >= 2560) {
+    AddBitStream(dest_buf, dest_bitpos, 0x1f, 12);
+    run -= 2560;
   }
-  return FALSE;
+  if (run >= 64) {
+    int markup = run - run % 64;
+    const uint8_t* p = bWhite ? WhiteRunMarkup : BlackRunMarkup;
+    p += (markup / 64 - 1) * 2;
+    AddBitStream(dest_buf, dest_bitpos, *p, p[1]);
+  }
+  run %= 64;
+  const uint8_t* p = bWhite ? WhiteRunTerminator : BlackRunTerminator;
+  p += run * 2;
+  AddBitStream(dest_buf, dest_bitpos, *p, p[1]);
 }
-FX_BOOL _FaxGet1DLine(const uint8_t* src_buf,
-                      int bitsize,
-                      int& bitpos,
-                      uint8_t* dest_buf,
-                      int columns) {
-  int color = TRUE;
-  int startpos = 0;
+
+void FaxEncode2DLine(uint8_t* dest_buf,
+                     int& dest_bitpos,
+                     const uint8_t* src_buf,
+                     const uint8_t* ref_buf,
+                     int cols) {
+  int a0 = -1;
+  bool a0color = true;
   while (1) {
-    if (bitpos >= bitsize) {
-      return FALSE;
-    }
-    int run_len = 0;
-    while (1) {
-      int run = _FaxGetRun(color ? FaxWhiteRunIns : FaxBlackRunIns, src_buf,
-                           bitpos, bitsize);
-      if (run < 0) {
-        while (bitpos < bitsize) {
-          int bit = NEXTBIT;
-          if (bit) {
-            return TRUE;
-          }
-        }
-        return FALSE;
+    int a1 = FindBit(src_buf, cols, a0 + 1, !a0color);
+    int b1, b2;
+    FaxG4FindB1B2(ref_buf, cols, a0, a0color, b1, b2);
+    if (b2 < a1) {
+      dest_bitpos += 3;
+      dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
+      dest_bitpos++;
+      a0 = b2;
+    } else if (a1 - b1 <= 3 && b1 - a1 <= 3) {
+      int delta = a1 - b1;
+      switch (delta) {
+        case 0:
+          dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
+          break;
+        case 1:
+        case 2:
+        case 3:
+          dest_bitpos += delta == 1 ? 1 : delta + 2;
+          dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
+          dest_bitpos++;
+          dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
+          break;
+        case -1:
+        case -2:
+        case -3:
+          dest_bitpos += delta == -1 ? 1 : -delta + 2;
+          dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
+          dest_bitpos++;
+          break;
       }
-      run_len += run;
-      if (run < 64) {
-        break;
+      dest_bitpos++;
+      a0 = a1;
+      a0color = !a0color;
+    } else {
+      int a2 = FindBit(src_buf, cols, a1 + 1, a0color);
+      dest_bitpos++;
+      dest_bitpos++;
+      dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
+      dest_bitpos++;
+      if (a0 < 0) {
+        a0 = 0;
       }
+      FaxEncodeRun(dest_buf, dest_bitpos, a1 - a0, a0color);
+      FaxEncodeRun(dest_buf, dest_bitpos, a2 - a1, !a0color);
+      a0 = a2;
     }
-    if (!color) {
-      _FaxFillBits(dest_buf, columns, startpos, startpos + run_len);
-    }
-    startpos += run_len;
-    if (startpos >= columns) {
-      break;
+    if (a0 >= cols) {
+      return;
     }
-    color = !color;
   }
-  return TRUE;
 }
 
+}  // namespace
+
 class CCodec_FaxDecoder : public CCodec_ScanlineDecoder {
  public:
   CCodec_FaxDecoder();
@@ -535,30 +490,30 @@ FX_BOOL CCodec_FaxDecoder::v_Rewind() {
 }
 uint8_t* CCodec_FaxDecoder::v_GetNextLine() {
   int bitsize = m_SrcSize * 8;
-  _FaxSkipEOL(m_pSrcBuf, bitsize, bitpos);
+  FaxSkipEOL(m_pSrcBuf, bitsize, bitpos);
   if (bitpos >= bitsize) {
     return NULL;
   }
   FXSYS_memset(m_pScanlineBuf, 0xff, m_Pitch);
   if (m_Encoding < 0) {
-    _FaxG4GetRow(m_pSrcBuf, bitsize, bitpos, m_pScanlineBuf, m_pRefBuf,
-                 m_OrigWidth);
+    FaxG4GetRow(m_pSrcBuf, bitsize, bitpos, m_pScanlineBuf, m_pRefBuf,
+                m_OrigWidth);
     FXSYS_memcpy(m_pRefBuf, m_pScanlineBuf, m_Pitch);
   } else if (m_Encoding == 0) {
-    _FaxGet1DLine(m_pSrcBuf, bitsize, bitpos, m_pScanlineBuf, m_OrigWidth);
+    FaxGet1DLine(m_pSrcBuf, bitsize, bitpos, m_pScanlineBuf, m_OrigWidth);
   } else {
     FX_BOOL bNext1D = m_pSrcBuf[bitpos / 8] & (1 << (7 - bitpos % 8));
     bitpos++;
     if (bNext1D) {
-      _FaxGet1DLine(m_pSrcBuf, bitsize, bitpos, m_pScanlineBuf, m_OrigWidth);
+      FaxGet1DLine(m_pSrcBuf, bitsize, bitpos, m_pScanlineBuf, m_OrigWidth);
     } else {
-      _FaxG4GetRow(m_pSrcBuf, bitsize, bitpos, m_pScanlineBuf, m_pRefBuf,
-                   m_OrigWidth);
+      FaxG4GetRow(m_pSrcBuf, bitsize, bitpos, m_pScanlineBuf, m_pRefBuf,
+                  m_OrigWidth);
     }
     FXSYS_memcpy(m_pRefBuf, m_pScanlineBuf, m_Pitch);
   }
   if (m_bEndOfLine) {
-    _FaxSkipEOL(m_pSrcBuf, bitsize, bitpos);
+    FaxSkipEOL(m_pSrcBuf, bitsize, bitpos);
   }
   if (m_bByteAlign && bitpos < bitsize) {
     int bitpos0 = bitpos;
@@ -589,14 +544,199 @@ FX_DWORD CCodec_FaxDecoder::GetSrcOffset() {
   }
   return ret;
 }
-extern "C" {
-void _FaxG4Decode(const uint8_t* src_buf,
-                  FX_DWORD src_size,
-                  int* pbitpos,
-                  uint8_t* dest_buf,
-                  int width,
-                  int height,
-                  int pitch) {
+
+FX_BOOL FaxSkipEOL(const uint8_t* src_buf, int bitsize, int& bitpos) {
+  int startbit = bitpos;
+  while (bitpos < bitsize) {
+    int bit = NEXTBIT;
+    if (bit) {
+      if (bitpos - startbit <= 11) {
+        bitpos = startbit;
+      }
+      return TRUE;
+    }
+  }
+  return FALSE;
+}
+
+FX_BOOL FaxGet1DLine(const uint8_t* src_buf,
+                     int bitsize,
+                     int& bitpos,
+                     uint8_t* dest_buf,
+                     int columns) {
+  bool color = true;
+  int startpos = 0;
+  while (1) {
+    if (bitpos >= bitsize) {
+      return FALSE;
+    }
+    int run_len = 0;
+    while (1) {
+      int run = FaxGetRun(color ? FaxWhiteRunIns : FaxBlackRunIns, src_buf,
+                          bitpos, bitsize);
+      if (run < 0) {
+        while (bitpos < bitsize) {
+          int bit = NEXTBIT;
+          if (bit) {
+            return TRUE;
+          }
+        }
+        return FALSE;
+      }
+      run_len += run;
+      if (run < 64) {
+        break;
+      }
+    }
+    if (!color) {
+      FaxFillBits(dest_buf, columns, startpos, startpos + run_len);
+    }
+    startpos += run_len;
+    if (startpos >= columns) {
+      break;
+    }
+    color = !color;
+  }
+  return TRUE;
+}
+
+FX_BOOL FaxG4GetRow(const uint8_t* src_buf,
+                    int bitsize,
+                    int& bitpos,
+                    uint8_t* dest_buf,
+                    const uint8_t* ref_buf,
+                    int columns) {
+  int a0 = -1;
+  bool a0color = true;
+  while (1) {
+    if (bitpos >= bitsize) {
+      return FALSE;
+    }
+    int a1, a2, b1, b2;
+    FaxG4FindB1B2(ref_buf, columns, a0, a0color, b1, b2);
+    FX_BOOL bit = NEXTBIT;
+    int v_delta = 0;
+    if (bit) {
+    } else {
+      if (bitpos >= bitsize) {
+        return FALSE;
+      }
+      FX_BOOL bit1 = NEXTBIT;
+      if (bitpos >= bitsize) {
+        return FALSE;
+      }
+      FX_BOOL bit2 = NEXTBIT;
+      if (bit1 && bit2) {
+        v_delta = 1;
+      } else if (bit1) {
+        v_delta = -1;
+      } else if (bit2) {
+        int run_len1 = 0;
+        while (1) {
+          int run = FaxGetRun(a0color ? FaxWhiteRunIns : FaxBlackRunIns,
+                              src_buf, bitpos, bitsize);
+          run_len1 += run;
+          if (run < 64) {
+            break;
+          }
+        }
+        if (a0 < 0) {
+          run_len1++;
+        }
+        a1 = a0 + run_len1;
+        if (!a0color) {
+          FaxFillBits(dest_buf, columns, a0, a1);
+        }
+        int run_len2 = 0;
+        while (1) {
+          int run = FaxGetRun(a0color ? FaxBlackRunIns : FaxWhiteRunIns,
+                              src_buf, bitpos, bitsize);
+          run_len2 += run;
+          if (run < 64) {
+            break;
+          }
+        }
+        a2 = a1 + run_len2;
+        if (a0color) {
+          FaxFillBits(dest_buf, columns, a1, a2);
+        }
+        a0 = a2;
+        if (a0 < columns) {
+          continue;
+        }
+        return TRUE;
+      } else {
+        if (bitpos >= bitsize) {
+          return FALSE;
+        }
+        bit = NEXTBIT;
+        if (bit) {
+          if (!a0color) {
+            FaxFillBits(dest_buf, columns, a0, b2);
+          }
+          if (b2 >= columns) {
+            return TRUE;
+          }
+          a0 = b2;
+          continue;
+        } else {
+          if (bitpos >= bitsize) {
+            return FALSE;
+          }
+          FX_BOOL bit1 = NEXTBIT;
+          if (bitpos >= bitsize) {
+            return FALSE;
+          }
+          FX_BOOL bit2 = NEXTBIT;
+          if (bit1 && bit2) {
+            v_delta = 2;
+          } else if (bit1) {
+            v_delta = -2;
+          } else if (bit2) {
+            if (bitpos >= bitsize) {
+              return FALSE;
+            }
+            bit = NEXTBIT;
+            if (bit) {
+              v_delta = 3;
+            } else {
+              v_delta = -3;
+            }
+          } else {
+            if (bitpos >= bitsize) {
+              return FALSE;
+            }
+            bit = NEXTBIT;
+            if (bit) {
+              bitpos += 3;
+              continue;
+            } else {
+              bitpos += 5;
+              return TRUE;
+            }
+          }
+        }
+      }
+    }
+    a1 = b1 + v_delta;
+    if (!a0color) {
+      FaxFillBits(dest_buf, columns, a0, a1);
+    }
+    if (a1 >= columns) {
+      return TRUE;
+    }
+    a0 = a1;
+    a0color = !a0color;
+  }
+}
+
+void FaxG4Decode(const uint8_t* src_buf,
+                 FX_DWORD src_size,
+                 int* pbitpos,
+                 uint8_t* dest_buf,
+                 int width,
+                 int height,
+                 int pitch) {
   if (pitch == 0) {
     pitch = (width + 7) / 8;
   }
@@ -606,139 +746,13 @@ void _FaxG4Decode(const uint8_t* src_buf,
   for (int iRow = 0; iRow < height; iRow++) {
     uint8_t* line_buf = dest_buf + iRow * pitch;
     FXSYS_memset(line_buf, 0xff, pitch);
-    _FaxG4GetRow(src_buf, src_size << 3, bitpos, line_buf, ref_buf, width);
+    FaxG4GetRow(src_buf, src_size << 3, bitpos, line_buf, ref_buf, width);
     FXSYS_memcpy(ref_buf, line_buf, pitch);
   }
   FX_Free(ref_buf);
   *pbitpos = bitpos;
 }
-};
-static const uint8_t BlackRunTerminator[128] = {
-    0x37, 10, 0x02, 3,  0x03, 2,  0x02, 2,  0x03, 3,  0x03, 4,  0x02, 4,
-    0x03, 5,  0x05, 6,  0x04, 6,  0x04, 7,  0x05, 7,  0x07, 7,  0x04, 8,
-    0x07, 8,  0x18, 9,  0x17, 10, 0x18, 10, 0x08, 10, 0x67, 11, 0x68, 11,
-    0x6c, 11, 0x37, 11, 0x28, 11, 0x17, 11, 0x18, 11, 0xca, 12, 0xcb, 12,
-    0xcc, 12, 0xcd, 12, 0x68, 12, 0x69, 12, 0x6a, 12, 0x6b, 12, 0xd2, 12,
-    0xd3, 12, 0xd4, 12, 0xd5, 12, 0xd6, 12, 0xd7, 12, 0x6c, 12, 0x6d, 12,
-    0xda, 12, 0xdb, 12, 0x54, 12, 0x55, 12, 0x56, 12, 0x57, 12, 0x64, 12,
-    0x65, 12, 0x52, 12, 0x53, 12, 0x24, 12, 0x37, 12, 0x38, 12, 0x27, 12,
-    0x28, 12, 0x58, 12, 0x59, 12, 0x2b, 12, 0x2c, 12, 0x5a, 12, 0x66, 12,
-    0x67, 12,
-};
-static const uint8_t BlackRunMarkup[80] = {
-    0x0f, 10, 0xc8, 12, 0xc9, 12, 0x5b, 12, 0x33, 12, 0x34, 12, 0x35, 12,
-    0x6c, 13, 0x6d, 13, 0x4a, 13, 0x4b, 13, 0x4c, 13, 0x4d, 13, 0x72, 13,
-    0x73, 13, 0x74, 13, 0x75, 13, 0x76, 13, 0x77, 13, 0x52, 13, 0x53, 13,
-    0x54, 13, 0x55, 13, 0x5a, 13, 0x5b, 13, 0x64, 13, 0x65, 13, 0x08, 11,
-    0x0c, 11, 0x0d, 11, 0x12, 12, 0x13, 12, 0x14, 12, 0x15, 12, 0x16, 12,
-    0x17, 12, 0x1c, 12, 0x1d, 12, 0x1e, 12, 0x1f, 12,
-};
-static const uint8_t WhiteRunTerminator[128] = {
-    0x35, 8, 0x07, 6, 0x07, 4, 0x08, 4, 0x0B, 4, 0x0C, 4, 0x0E, 4, 0x0F, 4,
-    0x13, 5, 0x14, 5, 0x07, 5, 0x08, 5, 0x08, 6, 0x03, 6, 0x34, 6, 0x35, 6,
-    0x2a, 6, 0x2B, 6, 0x27, 7, 0x0c, 7, 0x08, 7, 0x17, 7, 0x03, 7, 0x04, 7,
-    0x28, 7, 0x2B, 7, 0x13, 7, 0x24, 7, 0x18, 7, 0x02, 8, 0x03, 8, 0x1a, 8,
-    0x1b, 8, 0x12, 8, 0x13, 8, 0x14, 8, 0x15, 8, 0x16, 8, 0x17, 8, 0x28, 8,
-    0x29, 8, 0x2a, 8, 0x2b, 8, 0x2c, 8, 0x2d, 8, 0x04, 8, 0x05, 8, 0x0a, 8,
-    0x0b, 8, 0x52, 8, 0x53, 8, 0x54, 8, 0x55, 8, 0x24, 8, 0x25, 8, 0x58, 8,
-    0x59, 8, 0x5a, 8, 0x5b, 8, 0x4a, 8, 0x4b, 8, 0x32, 8, 0x33, 8, 0x34, 8,
-};
-static const uint8_t WhiteRunMarkup[80] = {
-    0x1b, 5,  0x12, 5,  0x17, 6,  0x37, 7,  0x36, 8,  0x37, 8,  0x64, 8,
-    0x65, 8,  0x68, 8,  0x67, 8,  0xcc, 9,  0xcd, 9,  0xd2, 9,  0xd3, 9,
-    0xd4, 9,  0xd5, 9,  0xd6, 9,  0xd7, 9,  0xd8, 9,  0xd9, 9,  0xda, 9,
-    0xdb, 9,  0x98, 9,  0x99, 9,  0x9a, 9,  0x18, 6,  0x9b, 9,  0x08, 11,
-    0x0c, 11, 0x0d, 11, 0x12, 12, 0x13, 12, 0x14, 12, 0x15, 12, 0x16, 12,
-    0x17, 12, 0x1c, 12, 0x1d, 12, 0x1e, 12, 0x1f, 12,
-};
-static void _AddBitStream(uint8_t* dest_buf,
-                          int& dest_bitpos,
-                          int data,
-                          int bitlen) {
-  for (int i = bitlen - 1; i >= 0; i--) {
-    if (data & (1 << i)) {
-      dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
-    }
-    dest_bitpos++;
-  }
-}
-static void _FaxEncodeRun(uint8_t* dest_buf,
-                          int& dest_bitpos,
-                          int run,
-                          FX_BOOL bWhite) {
-  while (run >= 2560) {
-    _AddBitStream(dest_buf, dest_bitpos, 0x1f, 12);
-    run -= 2560;
-  }
-  if (run >= 64) {
-    int markup = run - run % 64;
-    const uint8_t* p = bWhite ? WhiteRunMarkup : BlackRunMarkup;
-    p += (markup / 64 - 1) * 2;
-    _AddBitStream(dest_buf, dest_bitpos, *p, p[1]);
-  }
-  run %= 64;
-  const uint8_t* p = bWhite ? WhiteRunTerminator : BlackRunTerminator;
-  p += run * 2;
-  _AddBitStream(dest_buf, dest_bitpos, *p, p[1]);
-}
-static void _FaxEncode2DLine(uint8_t* dest_buf,
-                             int& dest_bitpos,
-                             const uint8_t* src_buf,
-                             const uint8_t* ref_buf,
-                             int cols) {
-  int a0 = -1, a0color = 1;
-  while (1) {
-    int a1 = _FindBit(src_buf, cols, a0 + 1, 1 - a0color);
-    int b1, b2;
-    _FaxG4FindB1B2(ref_buf, cols, a0, a0color, b1, b2);
-    if (b2 < a1) {
-      dest_bitpos += 3;
-      dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
-      dest_bitpos++;
-      a0 = b2;
-    } else if (a1 - b1 <= 3 && b1 - a1 <= 3) {
-      int delta = a1 - b1;
-      switch (delta) {
-        case 0:
-          dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
-          break;
-        case 1:
-        case 2:
-        case 3:
-          dest_bitpos += delta == 1 ? 1 : delta + 2;
-          dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
-          dest_bitpos++;
-          dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
-          break;
-        case -1:
-        case -2:
-        case -3:
-          dest_bitpos += delta == -1 ? 1 : -delta + 2;
-          dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
-          dest_bitpos++;
-          break;
-      }
-      dest_bitpos++;
-      a0 = a1;
-      a0color = 1 - a0color;
-    } else {
-      int a2 = _FindBit(src_buf, cols, a1 + 1, a0color);
-      dest_bitpos++;
-      dest_bitpos++;
-      dest_buf[dest_bitpos / 8] |= 1 << (7 - dest_bitpos % 8);
-      dest_bitpos++;
-      if (a0 < 0) {
-        a0 = 0;
-      }
-      _FaxEncodeRun(dest_buf, dest_bitpos, a1 - a0, a0color);
-      _FaxEncodeRun(dest_buf, dest_bitpos, a2 - a1, 1 - a0color);
-      a0 = a2;
-    }
-    if (a0 >= cols) {
-      return;
-    }
-  }
-}
+
 class CCodec_FaxEncoder {
  public:
   CCodec_FaxEncoder(const uint8_t* src_buf, int width, int height, int pitch);
@@ -775,7 +789,7 @@ void CCodec_FaxEncoder::Encode(uint8_t*& dest_buf, FX_DWORD& dest_size) {
     const uint8_t* scan_line = m_pSrcBuf + i * m_Pitch;
     FXSYS_memset(m_pLineBuf, 0, m_Pitch * 8);
     m_pLineBuf[0] = last_byte;
-    _FaxEncode2DLine(m_pLineBuf, dest_bitpos, scan_line, m_pRefLine, m_Cols);
+    FaxEncode2DLine(m_pLineBuf, dest_bitpos, scan_line, m_pRefLine, m_Cols);
     m_DestBuf.AppendBlock(m_pLineBuf, dest_bitpos / 8);
     last_byte = m_pLineBuf[dest_bitpos / 8];
     dest_bitpos %= 8;
diff --git a/core/src/fxcodec/jbig2/JBig2_Define.h b/core/src/fxcodec/jbig2/JBig2_Define.h
index 50516f5798..d1a19c5d61 100644
--- a/core/src/fxcodec/jbig2/JBig2_Define.h
+++ b/core/src/fxcodec/jbig2/JBig2_Define.h
@@ -26,16 +26,6 @@ struct JBig2HuffmanCode {
   int32_t code;
 };
 
-extern "C" {
-void _FaxG4Decode(const uint8_t* src_buf,
-                  FX_DWORD src_size,
-                  int* pbitpos,
-                  uint8_t* dest_buf,
-                  int width,
-                  int height,
-                  int pitch = 0);
-};
-
 #define JBIG2_MAX_REFERRED_SEGMENT_COUNT 64
 #define JBIG2_MAX_EXPORT_SYSMBOLS 65535
 #define JBIG2_MAX_NEW_SYSMBOLS 65535
diff --git a/core/src/fxcodec/jbig2/JBig2_GrdProc.cpp b/core/src/fxcodec/jbig2/JBig2_GrdProc.cpp
index 5eb0570e72..eda76bbce9 100644
--- a/core/src/fxcodec/jbig2/JBig2_GrdProc.cpp
+++ b/core/src/fxcodec/jbig2/JBig2_GrdProc.cpp
@@ -7,6 +7,7 @@
 #include "JBig2_GrdProc.h"
 
 #include "../../../../third_party/base/nonstd_unique_ptr.h"
+#include "../../../include/fxcodec/fx_codec.h"
 #include "JBig2_ArithDecoder.h"
 #include "JBig2_BitStream.h"
 #include "JBig2_Image.h"
@@ -668,8 +669,8 @@ FXCODEC_STATUS CJBig2_GRDProc::Start_decode_MMR(CJBig2_Image** pImage,
     return m_ProssiveStatus;
   }
   bitpos = (int)pStream->getBitPos();
-  _FaxG4Decode(pStream->getBuf(), pStream->getLength(), &bitpos,
-               (*pImage)->m_pData, GBW, GBH, (*pImage)->m_nStride);
+  FaxG4Decode(pStream->getBuf(), pStream->getLength(), &bitpos,
+              (*pImage)->m_pData, GBW, GBH, (*pImage)->m_nStride);
   pStream->setBitPos(bitpos);
   for (i = 0; (FX_DWORD)i < (*pImage)->m_nStride * GBH; i++) {
     (*pImage)->m_pData[i] = ~(*pImage)->m_pData[i];