decode: support multiple data segments.

Previously, the payload was assumed to consist of one large data
segment. Now, multiple segments of different types may be concatenated
together. The data type reported is the highest data type encountered
while decoding.

Author: dlbeer

lib/decode.c

@@ -394,6 +394,7 @@ static quirc_decode_error_t correct_format(uint16_t *f_ret)
 struct datastream {
 	uint8_t		raw[QUIRC_MAX_PAYLOAD];
 	int		data_bits;
+	int		ptr;
 
 	uint8_t         data[QUIRC_MAX_PAYLOAD];
 };
@@ -609,36 +610,41 @@ static quirc_decode_error_t codestream_ecc(struct quirc_data *data,
 	return QUIRC_SUCCESS;
 }
 
-static int get_bits(const uint8_t *data, int pos, int len)
+static inline int bits_remaining(const struct datastream *ds)
+{
+	return ds->data_bits - ds->ptr;
+}
+
+static int take_bits(struct datastream *ds, int len)
 {
 	int ret = 0;
 
-	while (len--) {
-		uint8_t b = data[pos >> 3];
-		int bitpos = pos & 7;
+	while (len && (ds->ptr < ds->data_bits)) {
+		uint8_t b = ds->data[ds->ptr >> 3];
+		int bitpos = ds->ptr & 7;
 
 		ret <<= 1;
 		if ((b << bitpos) & 0x80)
 			ret |= 1;
 
-		pos++;
+		ds->ptr++;
+		len--;
 	}
 
 	return ret;
 }
 
 static int numeric_tuple(struct quirc_data *data,
-			 const struct datastream *ds,
-			 int *ptr, int bits, int digits)
+			 struct datastream *ds,
+			 int bits, int digits)
 {
 	int tuple;
 	int i;
 
-	if (*ptr + bits > ds->data_bits)
+	if (bits_remaining(ds) < bits)
 		return -1;
 
-	tuple = get_bits(ds->data, *ptr, bits);
-	*ptr += bits;
+	tuple = take_bits(ds, bits);
 
 	for (i = digits - 1; i >= 0; i--) {
 		data->payload[data->payload_len + i] = tuple % 10 + '0';
@@ -654,48 +660,48 @@ static quirc_decode_error_t decode_numeric(struct quirc_data *data,
 {
 	int bits = 14;
 	int count;
-	int ptr;
 
 	if (data->version < 10)
 		bits = 10;
 	else if (data->version < 27)
 		bits = 12;
 
-	count = get_bits(ds->data, 4, bits);
-	if (count + 1 > QUIRC_MAX_PAYLOAD)
+	count = take_bits(ds, bits);
+	if (data->payload_len + count + 1 > QUIRC_MAX_PAYLOAD)
 		return QUIRC_ERROR_DATA_OVERFLOW;
 
-	data->payload_len = 0;
-	ptr = bits + 4;
-
-	while (data->payload_len + 2 < count)
-		if (numeric_tuple(data, ds, &ptr, 10, 3) < 0)
+	while (count >= 3) {
+		if (numeric_tuple(data, ds, 10, 3) < 0)
 			return QUIRC_ERROR_DATA_UNDERFLOW;
+		count -= 3;
+	}
 
-	if ((data->payload_len + 1 < count) &&
-	    (numeric_tuple(data, ds, &ptr, 7, 2) < 0))
-		return QUIRC_ERROR_DATA_UNDERFLOW;
+	if (count >= 2) {
+		if (numeric_tuple(data, ds, 7, 2) < 0)
+			return QUIRC_ERROR_DATA_UNDERFLOW;
+		count -= 2;
+	}
 
-	if ((data->payload_len < count) &&
-	    (numeric_tuple(data, ds, &ptr, 4, 1) < 0))
-		return QUIRC_ERROR_DATA_UNDERFLOW;
+	if (count) {
+		if (numeric_tuple(data, ds, 4, 1) < 0)
+			return QUIRC_ERROR_DATA_UNDERFLOW;
+		count--;
+	}
 
-	data->payload[count] = 0;
 	return QUIRC_SUCCESS;
 }
 
 static int alpha_tuple(struct quirc_data *data,
-		       const struct datastream *ds,
-		       int *ptr, int bits, int digits)
+		       struct datastream *ds,
+		       int bits, int digits)
 {
 	int tuple;
 	int i;
 
-	if (*ptr + bits > ds->data_bits)
+	if (bits_remaining(ds) < bits)
 		return -1;
 
-	tuple = get_bits(ds->data, *ptr, bits);
-	*ptr += bits;
+	tuple = take_bits(ds, bits);
 
 	for (i = 0; i < digits; i++) {
 		static const char *alpha_map =
@@ -715,29 +721,28 @@ static quirc_decode_error_t decode_alpha(struct quirc_data *data,
 {
 	int bits = 13;
 	int count;
-	int ptr;
 
 	if (data->version < 7)
 		bits = 9;
 	else if (data->version < 11)
 		bits = 10;
 
-	count = get_bits(ds->data, 4, bits);
-	if (count + 1 > QUIRC_MAX_PAYLOAD)
+	count = take_bits(ds, bits);
+	if (data->payload_len + count + 1 > QUIRC_MAX_PAYLOAD)
 		return QUIRC_ERROR_DATA_OVERFLOW;
 
-	data->payload_len = 0;
-	ptr = bits + 4;
-
-	while (data->payload_len + 1 < count)
-		if (alpha_tuple(data, ds, &ptr, 11, 2) < 0)
+	while (count >= 2) {
+		if (alpha_tuple(data, ds, 11, 2) < 0)
 			return QUIRC_ERROR_DATA_UNDERFLOW;
+		count -= 2;
+	}
 
-	if ((data->payload_len < count) &&
-	    (alpha_tuple(data, ds, &ptr, 6, 1) < 0))
-		return QUIRC_ERROR_DATA_UNDERFLOW;
+	if (count) {
+		if (alpha_tuple(data, ds, 6, 1) < 0)
+			return QUIRC_ERROR_DATA_UNDERFLOW;
+		count--;
+	}
 
-	data->payload[count] = 0;
 	return QUIRC_SUCCESS;
 }
 
@@ -751,17 +756,14 @@ static quirc_decode_error_t decode_byte(struct quirc_data *data,
 	if (data->version < 10)
 		bits = 8;
 
-	count = get_bits(ds->data, 4, bits);
-	if (count + 1 > QUIRC_MAX_PAYLOAD)
+	count = take_bits(ds, bits);
+	if (data->payload_len + count + 1 > QUIRC_MAX_PAYLOAD)
 		return QUIRC_ERROR_DATA_OVERFLOW;
-	if (count * 8 + bits + 4 > ds->data_bits)
+	if (bits_remaining(ds) < count * 8)
 		return QUIRC_ERROR_DATA_UNDERFLOW;
 
 	for (i = 0; i < count; i++)
-		data->payload[i] = get_bits(ds->data, i * 8 + bits + 4, 8);
-
-	data->payload[count] = 0;
-	data->payload_len = count;
+		data->payload[data->payload_len++] = take_bits(ds, 8);
 
 	return QUIRC_SUCCESS;
 }
@@ -778,51 +780,70 @@ static quirc_decode_error_t decode_kanji(struct quirc_data *data,
 	else if (data->version < 27)
 		bits = 10;
 
-	count = get_bits(ds->data, 4, bits);
-	if (count * 2 + 1 > QUIRC_MAX_PAYLOAD)
+	count = take_bits(ds, bits);
+	if (data->payload_len + count * 2 + 1 > QUIRC_MAX_PAYLOAD)
 		return QUIRC_ERROR_DATA_OVERFLOW;
-	if (count * 13 + bits + 4 > ds->data_bits)
+	if (bits_remaining(ds) < count * 13)
 		return QUIRC_ERROR_DATA_UNDERFLOW;
 
 	for (i = 0; i < count; i++) {
-		int d = get_bits(ds->data, i * 13 + bits + 4, 13);
+		int d = take_bits(ds, 13);
 		uint16_t sjw;
 
 		if (d + 0x8140 >= 0x9ffc)
 			sjw = d + 0x8140;
 		else
 			sjw = d + 0xc140;
 
-		data->payload[i * 2] = sjw >> 8;
-		data->payload[i * 2 + 1] = sjw & 0xff;
+		data->payload[data->payload_len++] = sjw >> 8;
+		data->payload[data->payload_len++] = sjw & 0xff;
 	}
 
-	data->payload[count * 2] = 0;
-	data->payload_len = count * 2;
-
 	return QUIRC_SUCCESS;
 }
 
 static quirc_decode_error_t decode_payload(struct quirc_data *data,
 					   struct datastream *ds)
 {
-	data->data_type = get_bits(ds->data, 0, 4);
+	while (bits_remaining(ds) >= 4) {
+		quirc_decode_error_t err = QUIRC_SUCCESS;
+		int type = take_bits(ds, 4);
+
+		switch (type) {
+		case QUIRC_DATA_TYPE_NUMERIC:
+			err = decode_numeric(data, ds);
+			break;
 
-	switch (data->data_type) {
-	case QUIRC_DATA_TYPE_NUMERIC:
-		return decode_numeric(data, ds);
+		case QUIRC_DATA_TYPE_ALPHA:
+			err = decode_alpha(data, ds);
+			break;
 
-	case QUIRC_DATA_TYPE_ALPHA:
-		return decode_alpha(data, ds);
+		case QUIRC_DATA_TYPE_BYTE:
+			err = decode_byte(data, ds);
+			break;
 
-	case QUIRC_DATA_TYPE_BYTE:
-		return decode_byte(data, ds);
+		case QUIRC_DATA_TYPE_KANJI:
+			err = decode_kanji(data, ds);
+			break;
 
-	case QUIRC_DATA_TYPE_KANJI:
-		return decode_kanji(data, ds);
+		default:
+			goto done;
+		}
+
+		if (err)
+			return err;
+
+		if (type > data->data_type)
+			data->data_type = type;
 	}
+done:
+
+	/* Add nul terminator to all payloads */
+	if (data->payload_len >= sizeof(data->payload))
+		data->payload_len--;
+	data->payload[data->payload_len] = 0;
 
-	return QUIRC_ERROR_UNKNOWN_DATA_TYPE;
+	return QUIRC_SUCCESS;
 }
 
 quirc_decode_error_t quirc_decode(const struct quirc_code *code,

lib/quirc.h

@@ -116,6 +116,10 @@ struct quirc_data {
 	int			version;
 	int			ecc_level;
 	int			mask;
+
+	/* This field is the highest-valued data type found in the QR
+	 * code.
+	 */
 	int			data_type;
 
 	/* Data payload. For the Kanji datatype, payload is encoded as