decoder template

skeletons/asn-decoder-template.c

+/*
+ * This is a generic BER decoder template for any ASN.1 type.
+ * 
+ * To compile, please redefine the asn_DEF as shown:
+ * 
+ *   cc -Dasn_DEF=asn_DEF_MyCustomType -o myTypeDecoder.o -c decoder-template.c
+ */
+#ifdef	HAVE_CONFIG_H
+#include <config.h>
+#endif
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>	/* for getopt */
+#include <string.h>	/* for strerror(3) */
+#include <errno.h>	/* for errno */
+#include <assert.h>	/* for assert(3) */
+#include <sysexits.h>	/* for EX_* exit codes */
+
+#include <constr_TYPE.h>
+
+extern asn_TYPE_descriptor_t asn_DEF;	/* ASN.1 type to be decoded */
+
+/*
+ * Open file and parse its BER contens.
+ */
+static void *data_decode_from_file(const char *fname, ssize_t suggested_bufsize);
+
+       int opt_debug;	/* -d */
+static int opt_check;	/* -c */
+static int opt_print;	/* -p */
+static int opt_stack;	/* -s */
+static int opt_toxml;	/* -x */
+
+#define	DEBUG(fmt, args...)	do {		\
+	if(!opt_debug) break;			\
+	fprintf(stderr, fmt, ##args);		\
+	fprintf(stderr, "\n");			\
+} while(0)
+
+int
+main(int ac, char **av) {
+	ssize_t suggested_bufsize = 8192;  /* close or equal to stdio buffer */
+	int number_of_iterations = 1;
+	int num;
+	int ch;
+
+	/*
+	 * Pocess the command-line argments.
+	 */
+	while((ch = getopt(ac, av, "b:cdn:hps:x")) != -1)
+	switch(ch) {
+	case 'b':
+		suggested_bufsize = atoi(optarg);
+		if(suggested_bufsize < 1
+			|| suggested_bufsize > 16 * 1024 * 1024) {
+			fprintf(stderr,
+				"-b %s: Improper buffer size (1..16M)\n",
+				optarg);
+			exit(EX_UNAVAILABLE);
+		}
+		break;
+	case 'c':
+		opt_check = 1;
+		break;
+	case 'd':
+		opt_debug++;	/* Double -dd means ASN.1 debug */
+		break;
+	case 'n':
+		number_of_iterations = atoi(optarg);
+		if(number_of_iterations < 1) {
+			fprintf(stderr,
+				"-n %s: Improper iterations count\n", optarg);
+			exit(EX_UNAVAILABLE);
+		}
+		break;
+	case 'p':
+		opt_print++;
+		break;
+	case 's':
+		opt_stack = atoi(optarg);
+		if(opt_stack <= 0) {
+			fprintf(stderr,
+				"-s %s: Value greater than 0 expected\n",
+				optarg);
+			exit(EX_UNAVAILABLE);
+		}
+		break;
+	case 'x':
+		opt_toxml++;
+		break;
+	case 'h':
+	default:
+		fprintf(stderr,
+		"Usage: %s [options] <data.ber> ...\n"
+		"Where options are:\n"
+		"  -b <size>    Set the i/o buffer size (default is %ld)\n"
+		"  -c           Check ASN.1 constraints after decoding\n"
+		"  -d           Enable debugging (-dd is even better)\n"
+		"  -n <num>     Process files <num> times\n"
+		"  -s <size>    Set the stack usage limit\n"
+		"  -p           Print out the decoded contents\n"
+		"  -x           Print out as XML\n"
+		, av[0], (long)suggested_bufsize);
+		exit(EX_USAGE);
+	}
+
+	ac -= optind;
+	av += optind;
+
+	if(ac < 1) {
+		fprintf(stderr, "Error: missing filename\n");
+		exit(EX_USAGE);
+	}
+
+	setvbuf(stdout, 0, _IOLBF, 0);
+
+	for(num = 0; num < number_of_iterations; num++) {
+	  int ac_i;
+	  /*
+	   * Process all files in turn.
+	   */
+	  for(ac_i = 0; ac_i < ac; ac_i++) {
+		char *fname = av[ac_i];
+		void *structure;
+
+		/*
+		 * Decode the encoded structure from file.
+		 */
+		structure = data_decode_from_file(fname, suggested_bufsize);
+		if(!structure) {
+			/* Error message is already printed */
+			exit(EX_DATAERR);
+		}
+
+		fprintf(stderr, "%s: decoded successfully\n", fname);
+
+		if(opt_print) asn_fprint(stdout, &asn_DEF, structure);
+
+		if(opt_toxml
+		&& xer_fprint(stdout, &asn_DEF, structure)) {
+			fprintf(stderr, "%s: Cannot convert into XML\n", fname);
+			exit(EX_UNAVAILABLE);
+		}
+
+		/* Check ASN.1 constraints */
+		if(opt_check) {
+			char errbuf[128];
+			size_t errlen = sizeof(errbuf);
+			if(asn_check_constraints(&asn_DEF, structure,
+				errbuf, &errlen)) {
+				fprintf(stderr, "%s: ASN.1 constraint "
+					"check failed: %s\n", fname, errbuf);
+				exit(EX_DATAERR);
+			}
+		}
+
+		asn_DEF.free_struct(&asn_DEF, structure, 0);
+	  }
+	}
+
+	return 0;
+}
+
+
+static char *buffer;
+static size_t buf_offset;	/* Offset from the start */
+static size_t buf_len;		/* Length of meaningful contents */
+static size_t buf_size;	/* Allocated memory */
+static off_t buf_shifted;	/* Number of bytes ever shifted */
+
+#define	bufptr	(buffer + buf_offset)
+#define	bufend	(buffer + buf_offset + buf_len)
+
+/*
+ * Ensure that the buffer contains at least this amoount of free space.
+ */
+static void buf_extend(size_t bySize) {
+
+	DEBUG("buf_extend(%ld) { o=%ld l=%ld s=%ld }",
+		(long)bySize, (long)buf_offset, (long)buf_len, (long)buf_size);
+
+	if(buf_size >= (buf_offset + buf_len + bySize)) {
+		return;	/* Nothing to do */
+	} else if(bySize <= buf_offset) {
+		DEBUG("\tContents shifted by %ld", (long)buf_offset);
+
+		/* Shift the buffer contents */
+		memmove(buffer, buffer + buf_offset, buf_len);
+		buf_shifted += buf_offset;
+		buf_offset = 0;
+	} else {
+		size_t newsize = (buf_size << 2) + bySize;
+		void *p = realloc(buffer, newsize);
+		if(p) {
+			buffer = p;
+			buf_size = newsize;
+
+			DEBUG("\tBuffer reallocated to %ld", (long)newsize);
+		} else {
+			perror("realloc()");
+			exit(EX_OSERR);
+		}
+	}
+}
+
+static void *data_decode_from_file(const char *fname, ssize_t suggested_bufsize) {
+	static char *fbuf;
+	static ssize_t fbuf_size;
+	static asn_codec_ctx_t s_codec_ctx;
+	asn_codec_ctx_t *opt_codec_ctx = 0;
+	void *structure = 0;
+	size_t rd;
+	FILE *fp;
+
+	if(opt_stack) {
+		s_codec_ctx.max_stack_size = opt_stack;
+		opt_codec_ctx = &s_codec_ctx;
+	}
+
+	DEBUG("Processing file %s", fname);
+
+	fp = fopen(fname, "r");
+
+	if(!fp) {
+		fprintf(stderr, "%s: %s\n", fname, strerror(errno));
+		return 0;
+	}
+
+	/* prepare the file buffer */
+	if(fbuf_size != suggested_bufsize) {
+		fbuf = realloc(fbuf, suggested_bufsize);
+		if(!fbuf) {
+			perror("realloc()");
+			exit(EX_OSERR);
+		}
+		fbuf_size = suggested_bufsize;
+	}
+
+	buf_shifted = 0;
+	buf_offset = 0;
+	buf_len = 0;
+
+	while((rd = fread(fbuf, 1, fbuf_size, fp)) || !feof(fp)) {
+		asn_dec_rval_t rval;
+		int using_local_buf;
+
+		/*
+		 * Copy the data over, or use the original buffer.
+		 */
+		if(buf_len) {
+			/* Append the new data into the intermediate buffer */
+			buf_extend(rd);
+			memcpy(bufend, fbuf, rd);
+			buf_len += rd;
+
+			rval = ber_decode(opt_codec_ctx, &asn_DEF,
+				(void **)&structure, bufptr, buf_len);
+			DEBUG("ber_decode(%ld) consumed %ld, code %d",
+				(long)buf_len, (long)rval.consumed, rval.code);
+
+			/*
+			 * Adjust position inside the source buffer.
+			 */
+			assert(rval.consumed <= buf_len);
+			buf_offset += rval.consumed;
+			buf_len -= rval.consumed;
+		} else {
+			using_local_buf = 1;
+
+			/* Feed the chunk of data into a BER decoder routine */
+			rval = ber_decode(opt_codec_ctx, &asn_DEF,
+				(void **)&structure, fbuf, rd);
+			DEBUG("ber_decode(%ld) consumed %ld, code %d",
+				(long)rd, (long)rval.consumed, rval.code);
+
+			/*
+			 * Switch the remainder into the intermediate buffer.
+			 */
+			if(rval.code != RC_FAIL && rval.consumed < rd) {
+				buf_extend(rd - rval.consumed);
+				memcpy(bufend,
+					fbuf + rval.consumed,
+					rd - rval.consumed);
+				buf_len = rd - rval.consumed;
+			}
+		}
+
+		switch(rval.code) {
+		case RC_OK:
+			DEBUG("RC_OK, finishing up");
+			fclose(fp);
+			return structure;
+		case RC_WMORE:
+			DEBUG("RC_WMORE, continuing...");
+			continue;
+		case RC_FAIL:
+			break;
+		}
+		break;
+	}
+
+	fclose(fp);
+
+	/* Clean up partially decoded structure */
+	asn_DEF.free_struct(&asn_DEF, structure, 0);
+
+	fprintf(stderr, "%s: "
+		"BER failure past %lld byte\n",
+		fname, (long long)(buf_shifted + buf_offset));
+
+	return 0;
+}
+

skeletons/file-dependencies

@@ -41,11 +41,11 @@ constr_SEQUENCE_OF.h constr_SEQUENCE_OF.c asn_SEQUENCE_OF.h constr_SET_OF.h
 constr_SET.h constr_SET.c
 constr_SET_OF.h constr_SET_OF.c asn_SET_OF.h
 
-COMMON-FILES:	# This is a special section
-asn_application.h
-asn_internal.h
-asn_codecs.h
+COMMON-FILES:			# THIS IS A SPECIAL SECTION
+asn_application.h		# Applications should include this file
 asn_system.h			# Platform-dependent types
+asn_codecs.h			# Return types of encoders and decoders
+asn_internal.h			# Internal stuff
 OCTET_STRING.h OCTET_STRING.c	# This one is used too widely
 BIT_STRING.h BIT_STRING.c	# This one is necessary for the above one
 asn_codecs_prim.c asn_codecs_prim.h	# enc/decoders for primitive types
@@ -58,3 +58,4 @@ constraints.h constraints.c	# Subtype constraints support
 xer_support.h xer_support.c	# XML parsing
 xer_decoder.h xer_decoder.c	# XER decoding support
 xer_encoder.h xer_encoder.c	# XER encoding support
+#asn-decoder-template.c		# Template for quick decoder creation