SkPDF: SkPDFFont organization changes.

SkPDFFont:
  - SkPDFType1Font::populate() encode advances correctly.
  - break out logically independent code into new files:
    * SkPDFConvertType1FontStream
    * SkPDFMakeToUnicodeCmap
    SkPDFFont.cpp is now 380 lines smaller.
    Expose `SkPDFAppendCmapSections()` for testing.

SkPDFFontImpl.h
  - Fold into SkPDFFont.

SkPDFConvertType1FontStream:
  - Now assume given a SkStreamAsset

SkPDFFont:
  - AdvanceMetric now hidden in a anonymous namespace.

No public API changes.
TBR=reed@google.com

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2221163002

Review-Url: https://codereview.chromium.org/2221163002

1 files changed, 205 insertions, 0 deletions

diff --git a/src/pdf/SkPDFConvertType1FontStream.cpp b/src/pdf/SkPDFConvertType1FontStream.cpp
new file mode 100644
index 0000000000..d75da5c787
--- /dev/null
+++ b/src/pdf/SkPDFConvertType1FontStream.cpp
@@ -0,0 +1,205 @@
+/*
+ * Copyright 2011 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPDFConvertType1FontStream.h"
+
+#include <ctype.h>
+
+static bool parsePFBSection(const uint8_t** src, size_t* len, int sectionType,
+                            size_t* size) {
+    // PFB sections have a two or six bytes header. 0x80 and a one byte
+    // section type followed by a four byte section length.  Type one is
+    // an ASCII section (includes a length), type two is a binary section
+    // (includes a length) and type three is an EOF marker with no length.
+    const uint8_t* buf = *src;
+    if (*len < 2 || buf[0] != 0x80 || buf[1] != sectionType) {
+        return false;
+    } else if (buf[1] == 3) {
+        return true;
+    } else if (*len < 6) {
+        return false;
+    }
+
+    *size = (size_t)buf[2] | ((size_t)buf[3] << 8) | ((size_t)buf[4] << 16) |
+            ((size_t)buf[5] << 24);
+    size_t consumed = *size + 6;
+    if (consumed > *len) {
+        return false;
+    }
+    *src = *src + consumed;
+    *len = *len - consumed;
+    return true;
+}
+
+static bool parsePFB(const uint8_t* src, size_t size, size_t* headerLen,
+                     size_t* dataLen, size_t* trailerLen) {
+    const uint8_t* srcPtr = src;
+    size_t remaining = size;
+
+    return parsePFBSection(&srcPtr, &remaining, 1, headerLen) &&
+           parsePFBSection(&srcPtr, &remaining, 2, dataLen) &&
+           parsePFBSection(&srcPtr, &remaining, 1, trailerLen) &&
+           parsePFBSection(&srcPtr, &remaining, 3, nullptr);
+}
+
+/* The sections of a PFA file are implicitly defined.  The body starts
+ * after the line containing "eexec," and the trailer starts with 512
+ * literal 0's followed by "cleartomark" (plus arbitrary white space).
+ *
+ * This function assumes that src is NUL terminated, but the NUL
+ * termination is not included in size.
+ *
+ */
+static bool parsePFA(const char* src, size_t size, size_t* headerLen,
+                     size_t* hexDataLen, size_t* dataLen, size_t* trailerLen) {
+    const char* end = src + size;
+
+    const char* dataPos = strstr(src, "eexec");
+    if (!dataPos) {
+        return false;
+    }
+    dataPos += strlen("eexec");
+    while ((*dataPos == '\n' || *dataPos == '\r' || *dataPos == ' ') &&
+            dataPos < end) {
+        dataPos++;
+    }
+    *headerLen = dataPos - src;
+
+    const char* trailerPos = strstr(dataPos, "cleartomark");
+    if (!trailerPos) {
+        return false;
+    }
+    int zeroCount = 0;
+    for (trailerPos--; trailerPos > dataPos && zeroCount < 512; trailerPos--) {
+        if (*trailerPos == '\n' || *trailerPos == '\r' || *trailerPos == ' ') {
+            continue;
+        } else if (*trailerPos == '0') {
+            zeroCount++;
+        } else {
+            return false;
+        }
+    }
+    if (zeroCount != 512) {
+        return false;
+    }
+
+    *hexDataLen = trailerPos - src - *headerLen;
+    *trailerLen = size - *headerLen - *hexDataLen;
+
+    // Verify that the data section is hex encoded and count the bytes.
+    int nibbles = 0;
+    for (; dataPos < trailerPos; dataPos++) {
+        if (isspace(*dataPos)) {
+            continue;
+        }
+        if (!isxdigit(*dataPos)) {
+            return false;
+        }
+        nibbles++;
+    }
+    *dataLen = (nibbles + 1) / 2;
+
+    return true;
+}
+
+static int8_t hexToBin(uint8_t c) {
+    if (!isxdigit(c)) {
+        return -1;
+    } else if (c <= '9') {
+        return c - '0';
+    } else if (c <= 'F') {
+        return c - 'A' + 10;
+    } else if (c <= 'f') {
+        return c - 'a' + 10;
+    }
+    return -1;
+}
+
+sk_sp<SkData> SkPDFConvertType1FontStream(
+        std::unique_ptr<SkStreamAsset> srcStream, size_t* headerLen,
+        size_t* dataLen, size_t* trailerLen) {
+    size_t srcLen = srcStream ? srcStream->getLength() : 0;
+    SkASSERT(srcLen);
+    if (!srcLen) {
+        return nullptr;
+    }
+    // Flatten and Nul-terminate the source stream so that we can use
+    // strstr() to search it.
+    SkAutoTMalloc<uint8_t> sourceBuffer(SkToInt(srcLen + 1));
+    (void)srcStream->read(sourceBuffer.get(), srcLen);
+    sourceBuffer[SkToInt(srcLen)] = 0;
+    const uint8_t* src = sourceBuffer.get();
+
+    if (parsePFB(src, srcLen, headerLen, dataLen, trailerLen)) {
+        static const int kPFBSectionHeaderLength = 6;
+        const size_t length = *headerLen + *dataLen + *trailerLen;
+        SkASSERT(length > 0);
+        SkASSERT(length + (2 * kPFBSectionHeaderLength) <= srcLen);
+
+        sk_sp<SkData> data(SkData::MakeUninitialized(length));
+
+        const uint8_t* const srcHeader = src + kPFBSectionHeaderLength;
+        // There is a six-byte section header before header and data
+        // (but not trailer) that we're not going to copy.
+        const uint8_t* const srcData = srcHeader + *headerLen + kPFBSectionHeaderLength;
+        const uint8_t* const srcTrailer = srcData + *headerLen;
+
+        uint8_t* const resultHeader = (uint8_t*)data->writable_data();
+        uint8_t* const resultData = resultHeader + *headerLen;
+        uint8_t* const resultTrailer = resultData + *dataLen;
+
+        SkASSERT(resultTrailer + *trailerLen == resultHeader + length);
+
+        memcpy(resultHeader,  srcHeader,  *headerLen);
+        memcpy(resultData,    srcData,    *dataLen);
+        memcpy(resultTrailer, srcTrailer, *trailerLen);
+
+        return data;
+    }
+
+    // A PFA has to be converted for PDF.
+    size_t hexDataLen;
+    if (!parsePFA((const char*)src, srcLen, headerLen, &hexDataLen, dataLen,
+                 trailerLen)) {
+        return nullptr;
+    }
+    const size_t length = *headerLen + *dataLen + *trailerLen;
+    SkASSERT(length > 0);
+    auto data = SkData::MakeUninitialized(length);
+    uint8_t* buffer = (uint8_t*)data->writable_data();
+
+    memcpy(buffer, src, *headerLen);
+    uint8_t* const resultData = &(buffer[*headerLen]);
+
+    const uint8_t* hexData = src + *headerLen;
+    const uint8_t* trailer = hexData + hexDataLen;
+    size_t outputOffset = 0;
+    uint8_t dataByte = 0;  // To hush compiler.
+    bool highNibble = true;
+    for (; hexData < trailer; hexData++) {
+        int8_t curNibble = hexToBin(*hexData);
+        if (curNibble < 0) {
+            continue;
+        }
+        if (highNibble) {
+            dataByte = curNibble << 4;
+            highNibble = false;
+        } else {
+            dataByte |= curNibble;
+            highNibble = true;
+            resultData[outputOffset++] = dataByte;
+        }
+    }
+    if (!highNibble) {
+        resultData[outputOffset++] = dataByte;
+    }
+    SkASSERT(outputOffset == *dataLen);
+
+    uint8_t* const resultTrailer = &(buffer[SkToInt(*headerLen + outputOffset)]);
+    memcpy(resultTrailer, src + *headerLen + hexDataLen, *trailerLen);
+    return data;
+}