SkOTUtils Struct Reference

#include <SkOTUtils.h>

Classes
class	LocalizedStrings_NameTable
class	LocalizedStrings_SingleName

Static Public Member Functions
static uint32_t	CalcTableChecksum (SK_OT_ULONG *data, size_t length)
static SkData *	RenameFont (SkStreamAsset *fontData, const char *fontName, int fontNameLen)
static void	SetAdvancedTypefaceFlags (SkOTTableOS2_V4::Type fsType, SkAdvancedTypefaceMetrics *info)

Detailed Description

Definition at line 20 of file SkOTUtils.h.

Member Function Documentation

CalcTableChecksum()

uint32_t SkOTUtils::CalcTableChecksum ( SK_OT_ULONG *  data, size_t  length  )

static

Calculates the OpenType checksum for data.

Definition at line 22 of file SkOTUtils.cpp.

                                                                      {
    uint32_t sum = 0;
    SK_OT_ULONG *dataEnd = data + ((length + 3) & ~3) / sizeof(SK_OT_ULONG);
    for (; data < dataEnd; ++data) {
        sum += SkEndian_SwapBE32(*data);
    }
    return sum;
}

RenameFont()

SkData * SkOTUtils::RenameFont ( SkStreamAsset *  fontData, const char *  fontName, int  fontNameLen  )

static

Renames an sfnt font. On failure (invalid data or not an sfnt font) returns nullptr.

Essentially, this removes any existing 'name' table and replaces it with a new one in which FontFamilyName, FontSubfamilyName, UniqueFontIdentifier, FullFontName, and PostscriptName are fontName.

The new 'name' table records will be written with the Windows, UnicodeBMPUCS2, and English_UnitedStates settings.

fontName and fontNameLen must be specified in terms of ASCII chars.

Does not affect fontData's ownership.

Definition at line 31 of file SkOTUtils.cpp.

                                                                                            {
 
    // Get the sfnt header.
    SkSFNTHeader sfntHeader;
    if (fontData->read(&sfntHeader, sizeof(sfntHeader)) < sizeof(sfntHeader)) {
        return nullptr;
    }
 
    // Find the existing 'name' table.
    int tableIndex;
    SkSFNTHeader::TableDirectoryEntry tableEntry;
    int numTables = SkEndian_SwapBE16(sfntHeader.numTables);
    for (tableIndex = 0; tableIndex < numTables; ++tableIndex) {
        if (fontData->read(&tableEntry, sizeof(tableEntry)) < sizeof(tableEntry)) {
            return nullptr;
        }
        if (SkOTTableName::TAG == tableEntry.tag) {
            break;
        }
    }
    if (tableIndex == numTables) {
        return nullptr;
    }
 
    if (!fontData->rewind()) {
        return nullptr;
    }
 
    // The required 'name' record types: Family, Style, Unique, Full and PostScript.
    static constexpr std::array<SkOTTableName::Record::NameID::Predefined::Value, 5> names{{
        SkOTTableName::Record::NameID::Predefined::FontFamilyName,
        SkOTTableName::Record::NameID::Predefined::FontSubfamilyName,
        SkOTTableName::Record::NameID::Predefined::UniqueFontIdentifier,
        SkOTTableName::Record::NameID::Predefined::FullFontName,
        SkOTTableName::Record::NameID::Predefined::PostscriptName,
    }};
 
    // GDI will not use a Symbol cmap table if there is no Symbol encoded name.
    static constexpr std::array<SkOTTableName::Record::EncodingID::Windows::Value, 2> encodings{{
        SkOTTableName::Record::EncodingID::Windows::Symbol,
        SkOTTableName::Record::EncodingID::Windows::UnicodeBMPUCS2,
    }};
 
    // Copy the data, leaving out the old name table.
    // In theory, we could also remove the DSIG table if it exists.
    size_t nameTableLogicalSize = sizeof(SkOTTableName)
                                + (encodings.size() * names.size() * sizeof(SkOTTableName::Record))
                                + (fontNameLen * sizeof(SK_OT_USHORT));
    size_t nameTablePhysicalSize = (nameTableLogicalSize + 3) & ~3; // Rounded up to a multiple of 4.
 
    size_t oldNameTablePhysicalSize = (SkEndian_SwapBE32(tableEntry.logicalLength) + 3) & ~3; // Rounded up to a multiple of 4.
    size_t oldNameTableOffset = SkEndian_SwapBE32(tableEntry.offset);
 
    //originalDataSize is the size of the original data without the name table.
    size_t originalDataSize = fontData->getLength() - oldNameTablePhysicalSize;
    size_t newDataSize = originalDataSize + nameTablePhysicalSize;
 
    auto rewrittenFontData = SkData::MakeUninitialized(newDataSize);
    SK_OT_BYTE* data = static_cast<SK_OT_BYTE*>(rewrittenFontData->writable_data());
 
    if (fontData->read(data, oldNameTableOffset) < oldNameTableOffset) {
        return nullptr;
    }
    if (fontData->skip(oldNameTablePhysicalSize) < oldNameTablePhysicalSize) {
        return nullptr;
    }
    if (fontData->read(data + oldNameTableOffset, originalDataSize - oldNameTableOffset) < originalDataSize - oldNameTableOffset) {
        return nullptr;
    }
 
    //Fix up the offsets of the directory entries after the old 'name' table entry.
    SkSFNTHeader::TableDirectoryEntry* currentEntry = reinterpret_cast<SkSFNTHeader::TableDirectoryEntry*>(data + sizeof(SkSFNTHeader));
    SkSFNTHeader::TableDirectoryEntry* endEntry = currentEntry + numTables;
    SkSFNTHeader::TableDirectoryEntry* headTableEntry = nullptr;
    for (; currentEntry < endEntry; ++currentEntry) {
        uint32_t oldOffset = SkEndian_SwapBE32(currentEntry->offset);
        if (oldOffset > oldNameTableOffset) {
            currentEntry->offset = SkEndian_SwapBE32(SkToU32(oldOffset - oldNameTablePhysicalSize));
        }
 
        if (SkOTTableHead::TAG == currentEntry->tag) {
            headTableEntry = currentEntry;
        }
    }
 
    // Make the table directory entry point to the new 'name' table.
    SkSFNTHeader::TableDirectoryEntry* nameTableEntry = reinterpret_cast<SkSFNTHeader::TableDirectoryEntry*>(data + sizeof(SkSFNTHeader)) + tableIndex;
    nameTableEntry->logicalLength = SkEndian_SwapBE32(SkToU32(nameTableLogicalSize));
    nameTableEntry->offset = SkEndian_SwapBE32(SkToU32(originalDataSize));
 
    // Write the new 'name' table after the original font data.
    SkOTTableName* nameTable = reinterpret_cast<SkOTTableName*>(data + originalDataSize);
    unsigned short stringOffset = sizeof(SkOTTableName) + (encodings.size() * names.size() * sizeof(SkOTTableName::Record));
    nameTable->format = SkOTTableName::format_0;
    nameTable->count = SkEndian_SwapBE16(encodings.size() * names.size());
    nameTable->stringOffset = SkEndian_SwapBE16(stringOffset);
 
    SkOTTableName::Record* nameRecord = reinterpret_cast<SkOTTableName::Record*>(data + originalDataSize + sizeof(SkOTTableName));
    for (const auto& encoding : encodings) {
        for (const auto& name : names) {
            nameRecord->platformID.value = SkOTTableName::Record::PlatformID::Windows;
            nameRecord->encodingID.windows.value = encoding;
            nameRecord->languageID.windows.value = SkOTTableName::Record::LanguageID::Windows::English_UnitedStates;
            nameRecord->nameID.predefined.value = name;
            nameRecord->offset = SkEndian_SwapBE16(0);
            nameRecord->length = SkEndian_SwapBE16(SkToU16(fontNameLen * sizeof(SK_OT_USHORT)));
            ++nameRecord;
        }
    }
 
    SK_OT_USHORT* nameString = reinterpret_cast<SK_OT_USHORT*>(data + originalDataSize + stringOffset);
    for (int i = 0; i < fontNameLen; ++i) {
        nameString[i] = SkEndian_SwapBE16(fontName[i]);
    }
 
    unsigned char* logical = data + originalDataSize + nameTableLogicalSize;
    unsigned char* physical = data + originalDataSize + nameTablePhysicalSize;
    for (; logical < physical; ++logical) {
        *logical = 0;
    }
 
    // Update the table checksum in the directory entry.
    nameTableEntry->checksum = SkEndian_SwapBE32(SkOTUtils::CalcTableChecksum(reinterpret_cast<SK_OT_ULONG*>(nameTable), nameTableLogicalSize));
 
    // Update the checksum adjustment in the head table.
    if (headTableEntry) {
        size_t headTableOffset = SkEndian_SwapBE32(headTableEntry->offset);
        if (headTableOffset + sizeof(SkOTTableHead) < originalDataSize) {
            SkOTTableHead* headTable = reinterpret_cast<SkOTTableHead*>(data + headTableOffset);
            headTable->checksumAdjustment = SkEndian_SwapBE32(0);
            uint32_t unadjustedFontChecksum = SkOTUtils::CalcTableChecksum(reinterpret_cast<SK_OT_ULONG*>(data), originalDataSize + nameTablePhysicalSize);
            headTable->checksumAdjustment = SkEndian_SwapBE32(SkOTTableHead::fontChecksum - unadjustedFontChecksum);
        }
    }
 
    return rewrittenFontData.release();
}

SetAdvancedTypefaceFlags()

void SkOTUtils::SetAdvancedTypefaceFlags ( SkOTTableOS2_V4::Type  fsType, SkAdvancedTypefaceMetrics *  info  )

static

Definition at line 219 of file SkOTUtils.cpp.

                                                                          {
    SkASSERT(info);
    // The logic should be identical to SkTypeface_FreeType::onGetAdvancedMetrics().
    if (fsType.raw.value != 0) {
        if (SkToBool(fsType.field.Restricted) || SkToBool(fsType.field.Bitmap)) {
            info->fFlags |= SkAdvancedTypefaceMetrics::kNotEmbeddable_FontFlag;
        }
        if (SkToBool(fsType.field.NoSubsetting)) {
            info->fFlags |= SkAdvancedTypefaceMetrics::kNotSubsettable_FontFlag;
        }
    }
}

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The documentation for this struct was generated from the following files:

• third_party/skia/src/sfnt/SkOTUtils.h
• third_party/skia/src/sfnt/SkOTUtils.cpp