decoder template
diff --git a/skeletons/asn-decoder-template.c b/skeletons/asn-decoder-template.c
new file mode 100644
index 0000000..aa893fb
--- /dev/null
+++ b/skeletons/asn-decoder-template.c
@@ -0,0 +1,313 @@
+/*
+ * 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;
+}
+