super-graph/jsn/keys.go

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// Package jsn provides fast and no-allocation functions to extract values and modify JSON data
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package jsn
// Keys function fetches all the unique keys in the JSON data in order of their occurance
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func Keys(b []byte) [][]byte {
res := make([][]byte, 0, 20)
s, e, d := 0, 0, 0
var k []byte
state := expectValue
st := newStack()
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ae := 0
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instr := false
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slash := 0
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for i := 0; i < len(b); i++ {
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if instr && b[i] == '\\' {
slash++
continue
}
if b[i] == '"' && (slash%2 == 0) {
instr = !instr
}
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if state == expectObjClose || state == expectListClose {
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if !instr {
switch b[i] {
case '{', '[':
d++
case '}', ']':
d--
}
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}
}
si := st.Peek()
switch {
case state == expectKey && si != nil && i >= si.ss:
i = si.se + 1
st.Pop()
case state == expectKey && b[i] == '{':
state = expectObjClose
s = i
d++
case state == expectObjClose && d == 0 && b[i] == '}':
state = expectKey
if ae != 0 {
st.Push(skipInfo{i, ae})
ae = 0
}
e = i
i = s
case state == expectKey && b[i] == '"':
state = expectKeyClose
s = i
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case state == expectKeyClose && (b[i] == '"' && (slash%2 == 0)):
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state = expectColon
k = b[(s + 1):i]
case state == expectColon && b[i] == ':':
state = expectValue
case state == expectValue && b[i] == '"':
state = expectString
s = i
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case state == expectString && (b[i] == '"' && (slash%2 == 0)):
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e = i
case state == expectValue && b[i] == '{':
state = expectObjClose
s = i
d++
case state == expectObjClose && d == 0 && b[i] == '}':
state = expectKey
e = i
i = s
case state == expectValue && b[i] == '[':
state = expectListClose
s = i
d++
case state == expectListClose && d == 0 && b[i] == ']':
state = expectKey
ae = i
e = i
i = s
case state == expectValue && (b[i] >= '0' && b[i] <= '9'):
state = expectNumClose
s = i
case state == expectNumClose &&
((b[i] < '0' || b[i] > '9') &&
(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 &&
(b[i] == 'f' || b[i] == 'F' || b[i] == 't' || b[i] == 'T'):
state = expectBoolClose
s = i
case state == expectBoolClose && (b[i] == 'e' || b[i] == 'E'):
e = i
case state == expectValue && b[i] == 'n':
state = expectNull
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s = i
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case state == expectNull && (b[i-1] == 'l' && b[i] == 'l'):
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e = i
}
if e != 0 {
if k != nil {
res = append(res, k)
}
if state == expectListClose {
loop:
for j := i + 1; j < len(b); j++ {
switch b[j] {
case ' ', '\t', '\n':
continue
case '{':
break loop
}
i = e
break loop
}
}
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state = expectKey
k = nil
e = 0
}
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slash = 0
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}
return res
}