font/sfnt: parse CFF 2-byte operators and real numbers.
Change-Id: I6f2cdfb44817832cf833883ef6fca692a001b6b1 Reviewed-on: https://go-review.googlesource.com/33813 Reviewed-by: Dave Day <djd@golang.org>
This commit is contained in:
Nigel Tao
parent
5286ed5c2a
commit
e2d0a9f0e6
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@ -20,9 +20,8 @@ package sfnt
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// - push the number 800
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// - FontBBox operator
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// - etc
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// defines a DICT that maps "version" to the String ID (SID) 379, the copyright
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// "Notice" to the SID 392, the font bounding box "FontBBox" to the four
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// numbers [100, 0, 500, 800], etc.
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// defines a DICT that maps "version" to the String ID (SID) 379, "Notice" to
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// the SID 392, "FontBBox" to the four numbers [100, 0, 500, 800], etc.
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//
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// The first 391 String IDs (starting at 0) are predefined as per the CFF spec
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// Appendix A, in 5176.CFF.pdf referenced below. For example, 379 means
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@ -50,6 +49,8 @@ package sfnt
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import (
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"fmt"
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"math"
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"strconv"
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)
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const (
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@ -80,10 +81,13 @@ type cffParser struct {
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base int
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offset int
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end int
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buf []byte
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err error
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buf []byte
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locBuf [2]uint32
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parseNumberBuf [maxRealNumberStrLen]byte
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instructions []byte
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stack struct {
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@ -265,8 +269,12 @@ func (p *cffParser) parseIndexLocations(dst []uint32, count, offSize int32) (ok
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// stack or executing an operator.
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func (p *cffParser) step() {
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if number, res := p.parseNumber(); res != prNone {
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if res == prBad || p.stack.top == psStackSize {
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p.err = errInvalidCFFTable
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if res < 0 || p.stack.top == psStackSize {
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if res == prUnsupportedRNE {
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p.err = errUnsupportedRealNumberEncoding
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} else {
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p.err = errInvalidCFFTable
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}
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return
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}
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p.stack.a[p.stack.top] = number
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@ -276,33 +284,54 @@ func (p *cffParser) step() {
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b0 := p.instructions[0]
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p.instructions = p.instructions[1:]
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if int(b0) < len(cff1ByteOperators) {
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if op := cff1ByteOperators[b0]; op.name != "" {
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if p.stack.top < op.numPop {
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for b, escaped, operators := b0, false, topDictOperators[0]; ; {
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if b == escapeByte && !escaped {
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if len(p.instructions) <= 0 {
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p.err = errInvalidCFFTable
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return
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}
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if op.run != nil {
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op.run(p)
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}
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if op.numPop < 0 {
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p.stack.top = 0
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} else {
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p.stack.top -= op.numPop
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}
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return
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b = p.instructions[0]
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p.instructions = p.instructions[1:]
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escaped = true
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operators = topDictOperators[1]
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continue
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}
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}
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p.err = fmt.Errorf("sfnt: unrecognized CFF 1-byte operator %d", b0)
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if int(b) < len(operators) {
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if op := operators[b]; op.name != "" {
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if p.stack.top < op.numPop {
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p.err = errInvalidCFFTable
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return
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}
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if op.run != nil {
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op.run(p)
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}
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if op.numPop < 0 {
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p.stack.top = 0
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} else {
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p.stack.top -= op.numPop
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}
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return
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}
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}
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if escaped {
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p.err = fmt.Errorf("sfnt: unrecognized CFF 2-byte operator (12 %d)", b)
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} else {
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p.err = fmt.Errorf("sfnt: unrecognized CFF 1-byte operator (%d)", b)
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}
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return
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}
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}
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type parseResult int32
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const (
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prBad parseResult = -1
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prNone parseResult = +0
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prGood parseResult = +1
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prUnsupportedRNE parseResult = -2
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prInvalid parseResult = -1
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prNone parseResult = +0
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prGood parseResult = +1
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)
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// See 5176.CFF.pdf section 4 "DICT Data".
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@ -314,7 +343,7 @@ func (p *cffParser) parseNumber() (number int32, res parseResult) {
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switch b0 := p.instructions[0]; {
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case b0 == 28:
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if len(p.instructions) < 3 {
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return 0, prBad
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return 0, prInvalid
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}
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number = int32(int16(u16(p.instructions[1:])))
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p.instructions = p.instructions[3:]
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@ -322,12 +351,48 @@ func (p *cffParser) parseNumber() (number int32, res parseResult) {
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case b0 == 29:
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if len(p.instructions) < 5 {
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return 0, prBad
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return 0, prInvalid
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}
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number = int32(u32(p.instructions[1:]))
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p.instructions = p.instructions[5:]
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return number, prGood
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case b0 == 30:
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// Parse a real number. This isn't listed in 5176.CFF.pdf Table 3
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// "Operand Encoding" but that table lists integer encodings. Further
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// down the page it says "A real number operand is provided in addition
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// to integer operands. This operand begins with a byte value of 30
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// followed by a variable-length sequence of bytes."
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s := p.parseNumberBuf[:0]
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p.instructions = p.instructions[1:]
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for {
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if len(p.instructions) == 0 {
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return 0, prInvalid
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}
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b := p.instructions[0]
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p.instructions = p.instructions[1:]
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// Process b's two nibbles, high then low.
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for i := 0; i < 2; i++ {
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nib := b >> 4
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b = b << 4
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if nib == 0x0f {
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f, err := strconv.ParseFloat(string(s), 32)
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if err != nil {
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return 0, prInvalid
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}
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return int32(math.Float32bits(float32(f))), prGood
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}
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if nib == 0x0d {
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return 0, prInvalid
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}
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if len(s)+maxNibbleDefsLength > len(p.parseNumberBuf) {
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return 0, prUnsupportedRNE
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}
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s = append(s, nibbleDefs[nib]...)
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}
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}
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case b0 < 32:
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// No-op.
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@ -337,7 +402,7 @@ func (p *cffParser) parseNumber() (number int32, res parseResult) {
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case b0 < 251:
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if len(p.instructions) < 2 {
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return 0, prBad
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return 0, prInvalid
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}
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b1 := p.instructions[1]
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p.instructions = p.instructions[2:]
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@ -345,7 +410,7 @@ func (p *cffParser) parseNumber() (number int32, res parseResult) {
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case b0 < 255:
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if len(p.instructions) < 2 {
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return 0, prBad
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return 0, prInvalid
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}
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b1 := p.instructions[1]
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p.instructions = p.instructions[2:]
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@ -355,6 +420,28 @@ func (p *cffParser) parseNumber() (number int32, res parseResult) {
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return 0, prNone
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}
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const maxNibbleDefsLength = len("E-")
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// nibbleDefs encodes 5176.CFF.pdf Table 5 "Nibble Definitions".
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var nibbleDefs = [16]string{
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0x00: "0",
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0x01: "1",
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0x02: "2",
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0x03: "3",
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0x04: "4",
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0x05: "5",
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0x06: "6",
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0x07: "7",
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0x08: "8",
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0x09: "9",
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0x0a: ".",
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0x0b: "E",
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0x0c: "E-",
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0x0d: "",
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0x0e: "-",
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0x0f: "",
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}
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type cffOperator struct {
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// numPop is the number of stack values to pop. -1 means "array" and -2
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// means "delta" as per 5176.CFF.pdf Table 6 "Operand Types".
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@ -367,9 +454,11 @@ type cffOperator struct {
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run func(*cffParser)
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}
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// cff1ByteOperators encodes the subset of 5176.CFF.pdf Table 9 "Top DICT
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// Operator Entries" used by this implementation.
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var cff1ByteOperators = [...]cffOperator{
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// topDictOperators encodes the subset of 5176.CFF.pdf Table 9 "Top DICT
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// Operator Entries" and Table 10 "CIDFont Operator Extensions" used by this
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// implementation.
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var topDictOperators = [2][]cffOperator{{
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// 1-byte operators.
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0: {+1, "version", nil},
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1: {+1, "Notice", nil},
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2: {+1, "FullName", nil},
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@ -384,6 +473,32 @@ var cff1ByteOperators = [...]cffOperator{
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p.saved.charStrings = p.stack.a[p.stack.top-1]
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}},
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18: {+2, "Private", nil},
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}
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}, {
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// 2-byte operators. The first byte is the escape byte.
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0: {+1, "Copyright", nil},
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1: {+1, "isFixedPitch", nil},
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2: {+1, "ItalicAngle", nil},
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3: {+1, "UnderlinePosition", nil},
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4: {+1, "UnderlineThickness", nil},
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5: {+1, "PaintType", nil},
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6: {+1, "CharstringType", nil},
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7: {-1, "FontMatrix", nil},
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8: {+1, "StrokeWidth", nil},
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20: {+1, "SyntheticBase", nil},
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21: {+1, "PostScript", nil},
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22: {+1, "BaseFontName", nil},
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23: {-2, "BaseFontBlend", nil},
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30: {+3, "ROS", nil},
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31: {+1, "CIDFontVersion", nil},
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32: {+1, "CIDFontRevision", nil},
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33: {+1, "CIDFontType", nil},
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34: {+1, "CIDCount", nil},
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35: {+1, "UIDBase", nil},
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36: {+1, "FDArray", nil},
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37: {+1, "FDSelect", nil},
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38: {+1, "FontName", nil},
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}}
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// TODO: 2-byte operators.
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// 5176.CFF.pdf section 4 "DICT Data" says that "Two-byte operators have an
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// initial escape byte of 12".
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const escapeByte = 12
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@ -22,7 +22,9 @@ import (
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// These constants are not part of the specifications, but are limitations used
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// by this implementation.
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const (
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maxNumTables = 256
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maxNumTables = 256
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maxRealNumberStrLen = 64 // Maximum length in bytes of the "-123.456E-7" representation.
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// (maxTableOffset + maxTableLength) will not overflow an int32.
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maxTableLength = 1 << 29
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maxTableOffset = 1 << 29
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@ -41,9 +43,10 @@ var (
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errInvalidTableTagOrder = errors.New("sfnt: invalid table tag order")
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errInvalidVersion = errors.New("sfnt: invalid version")
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errUnsupportedCFFVersion = errors.New("sfnt: unsupported CFF version")
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errUnsupportedNumberOfTables = errors.New("sfnt: unsupported number of tables")
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errUnsupportedTableOffsetLength = errors.New("sfnt: unsupported table offset or length")
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errUnsupportedCFFVersion = errors.New("sfnt: unsupported CFF version")
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errUnsupportedRealNumberEncoding = errors.New("sfnt: unsupported real number encoding")
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errUnsupportedNumberOfTables = errors.New("sfnt: unsupported number of tables")
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errUnsupportedTableOffsetLength = errors.New("sfnt: unsupported table offset or length")
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)
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// Units are an integral number of abstract, scalable "font units". The em
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BIN
font/testdata/CFFTest.otf
vendored
BIN
font/testdata/CFFTest.otf
vendored
Binary file not shown.
4
font/testdata/CFFTest.sfd
vendored
4
font/testdata/CFFTest.sfd
vendored
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@ -5,7 +5,7 @@ FamilyName: CFFTest
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Weight: Regular
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Copyright: Copyright 2016 The Go Authors. All rights reserved.\nUse of this font is governed by a BSD-style license that can be found at https://golang.org/LICENSE.
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Version: 001.000
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ItalicAngle: 0
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ItalicAngle: -11.25
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UnderlinePosition: -100
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UnderlineWidth: 50
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Ascent: 800
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@ -19,7 +19,7 @@ OS2Version: 0
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OS2_WeightWidthSlopeOnly: 0
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OS2_UseTypoMetrics: 1
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CreationTime: 1479626795
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ModificationTime: 1480238616
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ModificationTime: 1480661567
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PfmFamily: 17
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TTFWeight: 400
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TTFWidth: 5
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