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image: allow "?" wildcards when registering image formats.

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R=r, nigeltao_gnome
CC=golang-dev
https://golang.org/cl/4404041
This commit is contained in:
Nigel Tao 2011-04-14 09:56:42 +10:00
parent a2e286828b
commit 4c60569e7c
1 changed files with 18 additions and 4 deletions
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22
src/pkg/image/format.go
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@ -25,7 +25,8 @@ var formats []format
// RegisterFormat registers an image format for use by Decode.
// Name is the name of the format, like "jpeg" or "png".
// Magic is the magic prefix that identifies the format's encoding.
// Magic is the magic prefix that identifies the format's encoding. The magic
// string can contain "?" wildcards that each match any one byte.
// Decode is the function that decodes the encoded image.
// DecodeConfig is the function that decodes just its configuration.
func RegisterFormat(name, magic string, decode func(io.Reader) (Image, os.Error), decodeConfig func(io.Reader) (Config, os.Error)) {
@ -46,11 +47,24 @@ func asReader(r io.Reader) reader {
return bufio.NewReader(r)
}
// sniff determines the format of r's data.
// Match returns whether magic matches b. Magic may contain "?" wildcards.
func match(magic string, b []byte) bool {
if len(magic) != len(b) {
return false
}
for i, c := range b {
if magic[i] != c && magic[i] != '?' {
return false
}
}
return true
}
// Sniff determines the format of r's data.
func sniff(r reader) format {
for _, f := range formats {
s, err := r.Peek(len(f.magic))
if err == nil && string(s) == f.magic {
b, err := r.Peek(len(f.magic))
if err == nil && match(f.magic, b) {
return f
}
}