Package riff

▾ Example

Code:

package riff_test

import (
    "fmt"
    "io"
    "io/ioutil"
    "log"
    "strings"

    "golang.org/x/image/riff"
)

func ExampleReader() {
    formType, r, err := riff.NewReader(strings.NewReader(data))
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("RIFF(%s)\n", formType)
    if err := dump(r, ".\t"); err != nil {
        log.Fatal(err)
    }
    // Output:
    // RIFF(ROOT)
    // .	ZERO ""
    // .	ONE  "a"
    // .	LIST(META)
    // .	.	LIST(GOOD)
    // .	.	.	ONE  "a"
    // .	.	.	FIVE "klmno"
    // .	.	ZERO ""
    // .	.	LIST(BAD )
    // .	.	.	THRE "def"
    // .	TWO  "bc"
    // .	LIST(UGLY)
    // .	.	FOUR "ghij"
    // .	.	SIX  "pqrstu"
}

func dump(r *riff.Reader, indent string) error {
    for {
        chunkID, chunkLen, chunkData, err := r.Next()
        if err == io.EOF {
            return nil
        }
        if err != nil {
            return err
        }
        if chunkID == riff.LIST {
            listType, list, err := riff.NewListReader(chunkLen, chunkData)
            if err != nil {
                return err
            }
            fmt.Printf("%sLIST(%s)\n", indent, listType)
            if err := dump(list, indent+".\t"); err != nil {
                return err
            }
            continue
        }
        b, err := ioutil.ReadAll(chunkData)
        if err != nil {
            return err
        }
        fmt.Printf("%s%s %q\n", indent, chunkID, b)
    }
}

func encodeU32(u uint32) string {
    return string([]byte{
        byte(u >> 0),
        byte(u >> 8),
        byte(u >> 16),
        byte(u >> 24),
    })
}

func encode(chunkID, contents string) string {
    n := len(contents)
    if n&1 == 1 {
        contents += "\x00"
    }
    return chunkID + encodeU32(uint32(n)) + contents
}

func encodeMulti(typ0, typ1 string, chunks ...string) string {
    n := 4
    for _, c := range chunks {
        n += len(c)
    }
    s := typ0 + encodeU32(uint32(n)) + typ1
    for _, c := range chunks {
        s += c
    }
    return s
}

var (
    d0   = encode("ZERO", "")
    d1   = encode("ONE ", "a")
    d2   = encode("TWO ", "bc")
    d3   = encode("THRE", "def")
    d4   = encode("FOUR", "ghij")
    d5   = encode("FIVE", "klmno")
    d6   = encode("SIX ", "pqrstu")
    l0   = encodeMulti("LIST", "GOOD", d1, d5)
    l1   = encodeMulti("LIST", "BAD ", d3)
    l2   = encodeMulti("LIST", "UGLY", d4, d6)
    l01  = encodeMulti("LIST", "META", l0, d0, l1)
    data = encodeMulti("RIFF", "ROOT", d0, d1, l01, d2, l2)
)