android jni检测 char utf8

JNI WARNING: input is not valid Modified UTF-8: illegal start byte

在加解密可能会出现非utf8字符

导致vm挂掉，所以需要在 NewStringUTF之前验证char*是不是含有非utf8字符

从vm扣除可用源码

typedef uint8_t         jboolean;       /* unsigned 8 bits */

类型

typedef u1 uint8_t;         

   static u1 checkUtfBytes(const char* bytes, const char** errorKind) {
        while (*bytes != '\0') {
            u1 utf8 = *(bytes++);
            // Switch on the high four bits.
            switch (utf8 >> 4) {
            case 0x00:
            case 0x01:
            case 0x02:
            case 0x03:
            case 0x04:
            case 0x05:
            case 0x06:
            case 0x07:
                // Bit pattern 0xxx. No need for any extra bytes.
                break;
            case 0x08:
            case 0x09:
            case 0x0a:
            case 0x0b:
            case 0x0f:
                /*
                 * Bit pattern 10xx or 1111, which are illegal start bytes.
                 * Note: 1111 is valid for normal UTF-8, but not the
                 * modified UTF-8 used here.
                 */
                *errorKind = "start";
                return utf8;
            case 0x0e:
                // Bit pattern 1110, so there are two additional bytes.
                utf8 = *(bytes++);
                if ((utf8 & 0xc0) != 0x80) {
                    *errorKind = "continuation";
                    return utf8;
                }
                // Fall through to take care of the final byte.
            case 0x0c:
            case 0x0d:
                // Bit pattern 110x, so there is one additional byte.
                utf8 = *(bytes++);
                if ((utf8 & 0xc0) != 0x80) {
                    *errorKind = "continuation";
                    return utf8;
                }
                break;
            }
        }
        return 0;
    }

验证函数是上面的

    const char* errorKind = NULL;
        u1 utf8 = checkUtfBytes(bytes, &errorKind);
        if (errorKind != NULL) {
            ALOGW("JNI WARNING: input is not valid Modified UTF-8: illegal %s byte %#x", errorKind, utf8);
            ALOGW("             string: '%s'", bytes);
            showLocation();
            abortMaybe();
        }

使用：把char和 errorKind传入

如果errorKind不为NULL说明含有非utf-8代码。做相应处理