Refactor Name with parseCmap.
This commit is contained in:
Steven Edwards
parent
a05e60ea09
commit
b78feafacd
1 changed files with 68 additions and 96 deletions
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@ -51,6 +51,20 @@ const (
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NameIDSampleText = 19
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)
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const (
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cmapFormat4 = 4
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cmapFormat12 = 12
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languageIndependent = 0
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// A 32-bit encoding consists of a most-significant 16-bit Platform ID and a
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// least-significant 16-bit Platform Specific ID. The magic numbers are
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// specified at https://www.microsoft.com/typography/otspec/name.htm
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unicodeEncoding = 0x00000003 // PID = 0 (Unicode), PSID = 3 (Unicode 2.0)
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microsoftSymbolEncoding = 0x00030000 // PID = 3 (Microsoft), PSID = 0 (Symbol)
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microsoftUCS2Encoding = 0x00030001 // PID = 3 (Microsoft), PSID = 1 (UCS-2)
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microsoftUCS4Encoding = 0x0003000a // PID = 3 (Microsoft), PSID = 10 (UCS-4)
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)
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// A Bounds holds the co-ordinate range of one or more glyphs.
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// The endpoints are inclusive.
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type Bounds struct {
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@ -143,6 +157,55 @@ func nameEntryInASCII(b []byte, utf16 bool) string {
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return string(buf)
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}
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// continueIf returns true if every b[offset]==values[i].
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func continueIf(b []byte, offsets, values []int) bool {
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for i, offset := range offsets {
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if int(u16(b, offset)) != values[i] {
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return false
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}
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}
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return true
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}
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// parseSubtables wraps the commonality in Name and parseCmap.
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func parseSubtables(b []byte, name string, firstSubtableOffset, subtableSize, valueOffset, valueLengthOffset int, offsets, values []int, isU16Offset bool) (int, int, int, error) {
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if len(b) < 4 {
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return 0, 0, 0, FormatError(name + " too short")
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}
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nsubtab := int(u16(b, 2))
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if len(b) < subtableSize*nsubtab+firstSubtableOffset {
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return 0, 0, 0, FormatError(name + " too short")
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}
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offset, length, pid, x := uint32(0), uint16(0), uint16(0), firstSubtableOffset
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for i := 0; i < nsubtab; i++ {
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if continueIf(b[x:], offsets, values) {
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// We read the 16-bit Platform ID and 16-bit Platform Specific ID as a single uint32.
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// All values are big-endian.
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pidPsid := u32(b, x)
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// We prefer the Unicode cmap encoding. Failing to find that, we fall
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// back onto the Microsoft cmap encoding.
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if pidPsid == unicodeEncoding {
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offset, length, pid = u32(b, x+valueOffset), u16(b, x+valueLengthOffset), uint16(pidPsid>>16)
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break
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} else if pidPsid == microsoftSymbolEncoding ||
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pidPsid == microsoftUCS2Encoding ||
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pidPsid == microsoftUCS4Encoding {
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offset, length, pid = u32(b, x+valueOffset), u16(b, x+valueLengthOffset), uint16(pidPsid>>16)
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// We don't break out of the for loop, so that Unicode can override Microsoft.
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}
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}
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x += subtableSize
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}
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if isU16Offset {
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offset >>= 16
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}
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return int(offset), int(length), int(pid), nil
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}
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const (
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locaOffsetFormatUnknown int = iota
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locaOffsetFormatShort
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@ -173,49 +236,9 @@ type Font struct {
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}
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func (f *Font) parseCmap() error {
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const (
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cmapFormat4 = 4
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cmapFormat12 = 12
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languageIndependent = 0
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// A 32-bit encoding consists of a most-significant 16-bit Platform ID and a
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// least-significant 16-bit Platform Specific ID. The magic numbers are
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// specified at https://www.microsoft.com/typography/otspec/name.htm
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unicodeEncoding = 0x00000003 // PID = 0 (Unicode), PSID = 3 (Unicode 2.0)
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microsoftSymbolEncoding = 0x00030000 // PID = 3 (Microsoft), PSID = 0 (Symbol)
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microsoftUCS2Encoding = 0x00030001 // PID = 3 (Microsoft), PSID = 1 (UCS-2)
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microsoftUCS4Encoding = 0x0003000a // PID = 3 (Microsoft), PSID = 10 (UCS-4)
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)
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if len(f.cmap) < 4 {
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return FormatError("cmap too short")
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}
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nsubtab := int(u16(f.cmap, 2))
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if len(f.cmap) < 8*nsubtab+4 {
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return FormatError("cmap too short")
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}
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offset, found, x := 0, false, 4
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for i := 0; i < nsubtab; i++ {
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// We read the 16-bit Platform ID and 16-bit Platform Specific ID as a single uint32.
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// All values are big-endian.
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pidPsid, o := u32(f.cmap, x), u32(f.cmap, x+4)
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x += 8
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// We prefer the Unicode cmap encoding. Failing to find that, we fall
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// back onto the Microsoft cmap encoding.
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if pidPsid == unicodeEncoding {
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offset, found = int(o), true
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break
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} else if pidPsid == microsoftSymbolEncoding ||
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pidPsid == microsoftUCS2Encoding ||
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pidPsid == microsoftUCS4Encoding {
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offset, found = int(o), true
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// We don't break out of the for loop, so that Unicode can override Microsoft.
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}
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}
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if !found {
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return UnsupportedError("cmap encoding")
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offset, _, _, err := parseSubtables(f.cmap, "cmap", 4, 8, 4, 0, []int{}, []int{}, false)
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if err != nil {
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return err
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}
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if offset <= 0 || offset > len(f.cmap) {
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return FormatError("bad cmap offset")
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@ -413,63 +436,12 @@ func (f *Font) Index(x rune) Index {
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// Name returns the NameID value of a Font.
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// Returns "" on error or not found.
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func (f *Font) Name(id NameID) string {
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const (
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cmapFormat4 = 4
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cmapFormat12 = 12
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languageIndependent = 0
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// A 32-bit encoding consists of a most-significant 16-bit Platform ID and a
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// least-significant 16-bit Platform Specific ID. The magic numbers are
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// specified at https://www.microsoft.com/typography/otspec/name.htm
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unicodeEncoding = 0x00000003 // PID = 0 (Unicode), PSID = 3 (Unicode 2.0)
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microsoftSymbolEncoding = 0x00030000 // PID = 3 (Microsoft), PSID = 0 (Symbol)
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microsoftUCS2Encoding = 0x00030001 // PID = 3 (Microsoft), PSID = 1 (UCS-2)
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microsoftUCS4Encoding = 0x0003000a // PID = 3 (Microsoft), PSID = 10 (UCS-4)
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)
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if len(f.name) < 18 { // The name table is three uint16s + at least one Name Record. Name Records are six uint16s.
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return ""
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}
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if u16(f.name, 0) != 0 { // The first uint16 in the name table should be set to 0, per the spec.
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return ""
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}
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numNames := int(u16(f.name, 2)) // The number of Name Records is the second uint16 in the name table.
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stringOffset := u16(f.name, 4) // And the offset marking the beginning of the character data is the third int16.
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if len(f.name) < int(stringOffset) {
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return ""
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}
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valueOffset, valueLength, pid := uint16(0), uint16(0), uint16(0)
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// Name Records begin at the fourth uint16 and are six uint16s long.
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for offset, i := 6, 0; i < numNames; i, offset = i+1, offset+12 {
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if u16(f.name, offset+8) == 0 { // Offset + 8 is the location of the string length. If zero, skip it.
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break
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}
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nameID := NameID(u16(f.name, offset+6))
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// Find the nameID of interest.
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if nameID == id {
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pidPsid := u32(f.name, offset)
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// We prefer the Unicode encoding. Failing to find that, we fall
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// back onto the Microsoft encoding.
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if pidPsid == unicodeEncoding {
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valueOffset, valueLength, pid = u16(f.name, offset+10), u16(f.name, offset+8), uint16(pidPsid>>16)
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break
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} else if pidPsid == microsoftSymbolEncoding ||
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pidPsid == microsoftUCS2Encoding ||
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pidPsid == microsoftUCS4Encoding {
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valueOffset, valueLength, pid = u16(f.name, offset+10), u16(f.name, offset+8), uint16(pidPsid>>16)
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// We don't break out of the for loop, so that Unicode can override Microsoft.
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}
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}
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}
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valueOffset, valueLength, pid, _ := parseSubtables(f.name, "name", 6, 12, 10, 8, []int{6}, []int{int(id)}, true)
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if valueOffset == 0 {
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return ""
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}
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stringOffset := int(u16(f.name, 4))
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// Return the ASCII value of the encoded string.
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// The string is encoded as UTF-16 on non-Apple pids; Apple is pid 1.
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return nameEntryInASCII(f.name[stringOffset+valueOffset:stringOffset+valueOffset+valueLength], pid != 1)
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