LIB-11: raw (low level) ISRC reads

CMakeLists.txt

@@ -36,7 +36,7 @@ CONFIGURE_FILE(${CMAKE_CURRENT_SOURCE_DIR}/libdiscid.pc.in ${CMAKE_CURRENT_BINAR
 CONFIGURE_FILE(${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile.in ${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile)
 
 IF(CMAKE_SYSTEM_NAME MATCHES "Linux")
-    SET(libdiscid_OSDEP_SRCS src/disc_linux.c)
+    SET(libdiscid_OSDEP_SRCS src/disc_linux.c src/disc_scsi.c)
 ELSEIF(CMAKE_SYSTEM_NAME MATCHES "Darwin")
     SET(libdiscid_OSDEP_SRCS src/disc_darwin.c)
     FIND_LIBRARY(COREFOUNDATION_LIBRARY CoreFoundation)

configure.ac

@@ -35,6 +35,9 @@ dnl The file containing the operating system dependent disc access code.
 if test "${os}" = "win32"; then
   DISC_OS_OBJ="disc_${os}.lo disc_${os}_new.lo"
   AC_MSG_NOTICE([using discid implementation disc_${os}.c disc_${os}_new.c])
+elif test "${os}" = "linux"; then
+  DISC_OS_OBJ="disc_${os}.lo disc_scsi.lo"
+  AC_MSG_NOTICE([using discid implementation disc_${os}.c disc_scsi.c])
 else
   DISC_OS_OBJ="disc_${os}.lo"
   AC_MSG_NOTICE([using discid implementation disc_${os}.c])

src/disc_linux.c

@@ -55,6 +55,7 @@
 
 /* TODO: make sure it's available */
 int snprintf(char *str, size_t size, const char *format, ...);
+void read_track_isrc_raw(int fd, mb_disc_private *disc, int track_num);
 
 
 static int read_toc_header(int fd, int *first, int *last) {
@@ -134,7 +135,7 @@ static void read_disc_mcn(int fd, mb_disc_private *disc)
 }
 
 /* Send a scsi command and receive data. */
-static int scsi_cmd(int fd, unsigned char *cmd, int cmd_len,
+int scsi_cmd(int fd, unsigned char *cmd, int cmd_len,
 		    const char *data, int data_len) {
 	int device_fd;
 	char sense_buffer[SG_MAX_SENSE]; /* for "error situations" */
@@ -173,11 +174,6 @@ static void read_track_isrc(int fd, mb_disc_private *disc, int track_num) {
 	memset(data, 0, sizeof data);
 	memset(buffer, 0, sizeof buffer);
 
-	/* data read from the last appropriate sector encountered
-	 * by a current or previous media access operation.
-	 * The Logical Unit accesses the media when there is/was no access.
-	 * TODO: force access at a specific block? -> no duplicate ISRCs?
-	 */
 	cmd[0] = 0x42;		/* READ SUB-CHANNEL */
 	/* cmd[1] reserved / MSF bit (unused) */
 	cmd[2] = 1 << 6;	/* 6th bit set (SUBQ) -> get sub-channel data */
@@ -257,7 +253,9 @@ int mb_disc_read_unportable(mb_disc_private *disc, const char *device) {
 		disc->track_offsets[i] = lba + 150;
 
 		/* Read the ISRC for the track */
-		read_track_isrc(fd, disc, i);
+		// TODO: test if raw actually is available
+		//read_track_isrc(fd, disc, i);
+		read_track_isrc_raw(fd, disc, i);
 	}
 
 	close(fd);

src/disc_scsi.c

@@ -0,0 +1,170 @@
+/* --------------------------------------------------------------------------
+
+   MusicBrainz -- The Internet music metadatabase
+
+   Copyright (C) 2013 Johannes Dewender
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+
+--------------------------------------------------------------------------- */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "discid/discid_private.h"
+
+/* Send a scsi command and receive data. */
+int scsi_cmd(int fd, unsigned char *cmd, int cmd_len,
+		    const char *data, int data_len);
+
+static void decode_isrc(unsigned char *q_channel, char *isrc) {
+	int isrc_pos;
+	int data_pos;
+	int bit_pos;
+	int bit;
+	unsigned char buffer;
+
+	isrc_pos = 0;
+	/* q_channel[0] = 0x03 -> mode 3 -> ISRC data */
+	data_pos = 1;
+	bit_pos = 7;
+	buffer = 0;
+	/* first 5 chars of ISRC are alphanumeric and 6-bit BCD encoded */
+	for (bit = 0; bit < 5*6; bit++) {
+		buffer = buffer << 1;
+		if ((q_channel[data_pos] & (1 << bit_pos)) == (1 << bit_pos)) {
+			buffer++;
+		}
+		bit_pos--;
+		if ((bit + 1)%8 == 0) {
+			bit_pos = 7;
+			data_pos++;
+		}
+		if ((bit + 1)%6 == 0) {
+			/* 0x3f = only lowest 6 bits set */
+			isrc[isrc_pos] = '0' + (buffer & 0x3f);
+			isrc_pos++;
+			buffer = 0;
+		}
+	}
+	/* buffer[4] includes 2 zero bits
+	 * last 7 chars of ISRC are only numeric and 4-bit encoded
+	 */
+	isrc[5] = '0' + (q_channel[5] >> 4);
+	isrc[6] = '0' + (q_channel[5] & 0x0f);
+	isrc[7] = '0' + (q_channel[6] >> 4);
+	isrc[8] = '0' + (q_channel[6] & 0x0f);
+	isrc[9] = '0' + (q_channel[7] >> 4);
+	isrc[10] = '0' + (q_channel[7] & 0x0f);
+	isrc[11] = '0' + (q_channel[8] >> 4);
+	/* q_channel[9] are zero bits
+	 * q_channel 10-12 are AFRAME
+	 */
+
+}
+
+void read_track_isrc_raw(int fd, mb_disc_private *disc, int track_num) {
+	/* there should be at least one ISRC in 100 sectors per spec
+	 * We try 150 (= 2 seconds) to be sure, but break when successfull
+	 */
+	const int SEC_NUM = 150;
+	unsigned char cmd[12];
+	unsigned char data[SEC_NUM*2448]; /* overall data */
+	unsigned char q_buffer;
+	unsigned char q_data[12]; /* sub-channel data in 1 sector */
+	char isrc[ISRC_STR_LENGTH+1];
+	unsigned long offset;
+	int char_num;
+	int sector;
+	int i;
+
+	memset(cmd, 0, sizeof cmd);
+	memset(data, 0, sizeof data);
+	memset(isrc, 0, sizeof isrc);
+
+	offset = disc->track_offsets[track_num];
+
+	/* 0xbe = READ CD, implementation optional in contrast to 0x42
+	 * support given with GET CONFIGURATION (0x46)
+	 * Support part of:
+	 * Multi-Read Feature (0x001d) and
+	 * CD Read Feature (0x001e),
+	 */
+	cmd[0] = 0xbe;	/* READ CD */
+	cmd[2] = offset >> 32;
+	cmd[3] = offset >> 16;
+	cmd[4] = offset >> 8;
+	cmd[5] = offset;  /* from where to start reading */
+	cmd[6] = SEC_NUM >> 16;
+	cmd[7] = SEC_NUM >> 8;
+	cmd[8] = SEC_NUM; /* sectors to read */
+	cmd[9] = 0xF8; 	/* 11111000 sync=1 all-header=11 user=1, ecc=1
+			 * no-error=00 */
+	cmd[10] = 0x01; 	/* Sub-Channel Selection raw P-W=001*/
+	/* cmd[11] = control byte */
+
+	if (scsi_cmd(fd, cmd, sizeof cmd, data, sizeof data) != 0) {
+		fprintf(stderr, "Warning: Cannot get ISRC code for track %d\n",
+			track_num);
+		return;
+	}
+
+	/* each sector has 96 bytes for one Q-channel type
+	 * We try until we finde an ISRC Q-channel
+	 */
+	for (sector = 0; sector < SEC_NUM; sector++) {
+		char_num = 0;
+		memset(q_data, 0, sizeof q_data);
+		q_buffer = 0;
+		/* the first 2352 bytes are raw data without sub-channels
+		 * We only want the 96 bit sub-channel data
+		 */
+		for (i = 2352; i < 2448; i++) {
+			q_buffer = q_buffer << 1;
+			/* the 6th bit is the Q-channel bit
+			 * we want to collect these bits
+			 */
+			if ((data[i + (sector*2448)] & (1 << 6)) == (1 << 6)) {
+				q_buffer++;
+			}
+			if ((i+1)%8 == 0) {
+				/* we have gathered one complete byte */
+				q_data[char_num] = q_buffer;
+				if (char_num == 0) {
+					/* test if we got the right type
+					 * of q-channel (ADR = 0x03)
+					 * upper 4 bit are CONTROL
+					 * Go to next sector otherwise
+					 */
+					if ((q_buffer & 0x0F) != 0x03) {
+						break;
+					}
+				}
+				char_num++;
+				q_buffer = 0;
+			}
+		}
+		if ((q_data[0] & 0x0F) == 0x03) {
+			/* we found a Q-channel with ISRC data */
+			decode_isrc(q_data, isrc);
+			break;
+		}
+	}
+	strncpy(disc->isrc[track_num], isrc, ISRC_STR_LENGTH);
+}
+
+
+/* EOF */