package jsn import ( "github.com/cespare/xxhash/v2" ) const ( expectKey int = iota expectKeyClose expectColon expectValue expectString expectNull expectListClose expectObjClose expectBoolClose expectNumClose ) type Field struct { Key []byte Value []byte } func Value(b []byte) []byte { e := (len(b) - 1) switch { case b[0] == '"' && b[e] == '"': return b[1:(len(b) - 1)] case b[0] == '[' && b[e] == ']': return nil case b[0] == '{' && b[e] == '}': return nil default: return b } } func Get(b []byte, keys [][]byte) []Field { kmap := make(map[uint64]struct{}, len(keys)) for i := range keys { kmap[xxhash.Sum64(keys[i])] = struct{}{} } res := make([]Field, 0, 20) s, e, d := 0, 0, 0 var k []byte state := expectKey n := 0 for i := 0; i < len(b); i++ { if state == expectObjClose || state == expectListClose { switch b[i] { case '{', '[': d++ case '}', ']': d-- } } switch { case state == expectKey && b[i] == '"': state = expectKeyClose s = i case state == expectKeyClose && b[i] == '"': state = expectColon k = b[(s + 1):i] case state == expectColon && b[i] == ':': state = expectValue case state == expectValue && b[i] == '"': state = expectString s = i case state == expectString && b[i] == '"': e = i case state == expectValue && b[i] == '[': state = expectListClose s = i d++ case state == expectListClose && d == 0 && b[i] == ']': e = i i = s case state == expectValue && b[i] == '{': state = expectObjClose s = i d++ case state == expectObjClose && d == 0 && b[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] != '-')): i-- e = i 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 case state == expectNull && b[i] == 'l': e = i } if e != 0 { _, ok := kmap[xxhash.Sum64(k)] if ok { res = append(res, Field{k, b[s:(e + 1)]}) n++ } state = expectKey e = 0 } } return res[:n] }