164 lines
2.9 KiB
Go
164 lines
2.9 KiB
Go
package jsn
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import (
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"bytes"
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"errors"
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"github.com/cespare/xxhash/v2"
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)
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func Replace(w *bytes.Buffer, b []byte, from, to []Field) error {
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if len(from) != len(to) {
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return errors.New("'from' and 'to' must be of the same length")
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}
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h := xxhash.New()
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tmap := make(map[uint64]int, len(from))
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for i, f := range from {
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h.Write(f.Key)
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h.Write(f.Value)
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tmap[h.Sum64()] = i
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h.Reset()
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}
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s, e, d := 0, 0, 0
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state := expectKey
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ws, we := -1, len(b)
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for i := 0; i < len(b); i++ {
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// skip any left padding whitespace
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if ws == -1 && (b[i] == '{' || b[i] == '[') {
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ws = i
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}
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if state == expectObjClose || state == expectListClose {
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switch b[i] {
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case '{', '[':
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d++
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case '}', ']':
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d--
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}
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}
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switch {
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case state == expectKey && b[i] == '"':
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state = expectKeyClose
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s = i
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case state == expectKeyClose && b[i] == '"':
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state = expectColon
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h.Write(b[(s + 1):i])
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we = s
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case state == expectColon && b[i] == ':':
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state = expectValue
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case state == expectValue && b[i] == '"':
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state = expectString
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s = i
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case state == expectString && b[i] == '"':
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e = i
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case state == expectValue && b[i] == '[':
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state = expectListClose
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s = i
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d++
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case state == expectListClose && d == 0 && b[i] == ']':
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e = i
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case state == expectValue && b[i] == '{':
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state = expectObjClose
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s = i
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d++
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case state == expectObjClose && d == 0 && b[i] == '}':
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e = i
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case state == expectValue && (b[i] >= '0' && b[i] <= '9'):
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state = expectNumClose
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s = i
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case state == expectNumClose &&
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((b[i] < '0' || b[i] > '9') &&
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(b[i] != '.' && b[i] != 'e' && b[i] != 'E' && b[i] != '+' && b[i] != '-')):
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e = i - 1
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case state == expectValue &&
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(b[i] == 'f' || b[i] == 'F' || b[i] == 't' || b[i] == 'T'):
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state = expectBoolClose
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s = i
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case state == expectBoolClose && (b[i] == 'e' || b[i] == 'E'):
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e = i
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case state == expectValue && b[i] == 'n':
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state = expectNull
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case state == expectNull && b[i] == 'l':
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e = i
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}
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if e != 0 {
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e++
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h.Write(b[s:e])
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n, ok := tmap[h.Sum64()]
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h.Reset()
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if ok {
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if _, err := w.Write(b[ws:(we + 1)]); err != nil {
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return err
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}
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if len(to[n].Key) != 0 {
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var err error
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if _, err := w.Write(to[n].Key); err != nil {
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return err
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}
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if _, err := w.WriteString(`":`); err != nil {
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return err
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}
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if len(to[n].Value) != 0 {
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_, err = w.Write(to[n].Value)
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} else {
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_, err = w.WriteString("null")
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}
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if err != nil {
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return err
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}
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ws = e
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} else if b[e] == ',' {
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ws = e + 1
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} else {
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ws = e
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}
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}
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if !ok && (b[s] == '[' || b[s] == '{') {
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// the i++ in the for loop will add 1 so we account for that (s - 1)
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i = s - 1
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}
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state = expectKey
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we = len(b)
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e = 0
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d = 0
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}
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}
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if ws == -1 || (ws == 0 && we == len(b)) {
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w.Write(b)
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} else if ws < we {
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w.Write(b[ws:we])
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}
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return nil
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}
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