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IterImplString.java
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151 lines (143 loc) · 6.32 KB
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package com.jsoniter;
import java.io.IOException;
import static java.lang.Character.*;
class IterImplString {
public static final String readString(JsonIterator iter) throws IOException {
byte c = IterImpl.nextToken(iter);
if (c == '"') {
// try fast path first
for (int i = iter.head, j = 0; i < iter.tail && j < iter.reusableChars.length; i++, j++) {
c = iter.buf[i];
if (c == '"') {
iter.head = i + 1;
return new String(iter.reusableChars, 0, j);
}
// If we encounter a backslash, which is a beginning of an escape sequence
// or a high bit was set - indicating an UTF-8 encoded multibyte character,
// there is no chance that we can decode the string without instantiating
// a temporary buffer, so quit this loop
if ((c ^ '\\') < 1) break;
iter.reusableChars[j] = (char) c;
}
return readStringSlowPath(iter);
}
if (c == 'n') {
IterImpl.skipUntilBreak(iter);
return null;
}
throw iter.reportError("readString", "expect n or \"");
}
final static String readStringSlowPath(JsonIterator iter) throws IOException {
// http://grepcode.com/file_/repository.grepcode.com/java/root/jdk/openjdk/8u40-b25/sun/nio/cs/UTF_8.java/?v=source
// byte => char with support of escape in one pass
int j = 0;
int minimumCapacity = iter.reusableChars.length - 2;
for (; ; ) {
if (j == minimumCapacity) {
char[] newBuf = new char[iter.reusableChars.length * 2];
System.arraycopy(iter.reusableChars, 0, newBuf, 0, iter.reusableChars.length);
iter.reusableChars = newBuf;
minimumCapacity = iter.reusableChars.length - 2;
}
int b1 = IterImpl.readByte(iter);
if (b1 >= 0) {
if (b1 == '"') {
return new String(iter.reusableChars, 0, j);
} else if (b1 == '\\') {
int b2 = IterImpl.readByte(iter);
switch (b2) {
case '"':
iter.reusableChars[j++] = '"';
break;
case '\\':
iter.reusableChars[j++] = '\\';
break;
case '/':
iter.reusableChars[j++] = '/';
break;
case 'b':
iter.reusableChars[j++] = '\b';
break;
case 'f':
iter.reusableChars[j++] = '\f';
break;
case 'n':
iter.reusableChars[j++] = '\n';
break;
case 'r':
iter.reusableChars[j++] = '\r';
break;
case 't':
iter.reusableChars[j++] = '\t';
break;
case 'u':
iter.reusableChars[j++] = IterImplNumber.readU4(iter);
break;
default:
throw iter.reportError("readStringSlowPath", "unexpected escape char: " + b2);
}
} else if (b1 == 0) {
throw iter.reportError("readStringSlowPath", "incomplete string");
} else {
// 1 byte, 7 bits: 0xxxxxxx
iter.reusableChars[j++] = (char) b1;
}
} else if ((b1 >> 5) == -2 && (b1 & 0x1e) != 0) {
// 2 bytes, 11 bits: 110xxxxx 10xxxxxx
int b2 = IterImpl.readByte(iter);
iter.reusableChars[j++] = (char) (((b1 << 6) ^ b2)
^
(((byte) 0xC0 << 6) ^
((byte) 0x80 << 0)));
} else if ((b1 >> 4) == -2) {
// 3 bytes, 16 bits: 1110xxxx 10xxxxxx 10xxxxxx
int b2 = IterImpl.readByte(iter);
int b3 = IterImpl.readByte(iter);
char c = (char)
((b1 << 12) ^
(b2 << 6) ^
(b3 ^
(((byte) 0xE0 << 12) ^
((byte) 0x80 << 6) ^
((byte) 0x80 << 0))));
iter.reusableChars[j++] = c;
} else if ((b1 >> 3) == -2) {
// 4 bytes, 21 bits: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
int b2 = IterImpl.readByte(iter);
int b3 = IterImpl.readByte(iter);
int b4 = IterImpl.readByte(iter);
int uc = ((b1 << 18) ^
(b2 << 12) ^
(b3 << 6) ^
(b4 ^
(((byte) 0xF0 << 18) ^
((byte) 0x80 << 12) ^
((byte) 0x80 << 6) ^
((byte) 0x80 << 0))));
iter.reusableChars[j++] = highSurrogate(uc);
iter.reusableChars[j++] = lowSurrogate(uc);
} else {
throw iter.reportError("readStringSlowPath", "unexpected input");
}
}
}
private static char highSurrogate(int codePoint) {
return (char) ((codePoint >>> 10)
+ (MIN_HIGH_SURROGATE - (MIN_SUPPLEMENTARY_CODE_POINT >>> 10)));
}
private static char lowSurrogate(int codePoint) {
return (char) ((codePoint & 0x3ff) + MIN_LOW_SURROGATE);
}
// slice does not allow escape
final static int findSliceEnd(JsonIterator iter) {
for (int i = iter.head; i < iter.tail; i++) {
byte c = iter.buf[i];
if (c == '"') {
return i + 1;
} else if (c == '\\') {
throw iter.reportError("findSliceEnd", "slice does not support escape char");
}
}
return -1;
}
}