input/trace32_ad: rephrase the header parse logic

There were several issues with the previous implementation of the logic
which parses trace32 input files: A string comparison was inverted, and
compared a seven character literal to a five character copy of the input.
One more character was trimmed before CTRL-Z (the CP/M EOF), which often
is SPACE in input files, but might be excessive on other input files.

Replace a DIY character search while we are here. Use symbolic names for
special characters. Factor out a test and memory release, to simplify
error code paths in the remaining logic. Extend comments.

diff --git a/src/input/trace32_ad.c b/src/input/trace32_ad.c
index 1f69028887b09a297bec438174430a205d94aa5c..f34a166db5fd48265a5a7381eaef0669902c5b93 100644 (file)
--- a/src/input/trace32_ad.c
+++ b/src/input/trace32_ad.c
@@ -49,6 +49,10 @@
 #define MAX_POD_COUNT     12
 #define HEADER_SIZE       80
 
+#define SPACE             ' '
+#define CTRLZ             '\x1a'
+#define TRACE32           "trace32"
+
 #define TIMESTAMP_RESOLUTION ((double)0.000000000078125) /* 0.078125 ns */
 
 /*
@@ -198,7 +202,8 @@ static int process_header(GString *buf, struct context *inc)
 {
        char *format_name, *format_name_sig;
        char *p;
-       int i, record_size, device_id;
+       int has_trace32;
+       int record_size, device_id;
 
        /*
         * 00-31 (0x00-1F) file format name
@@ -227,33 +232,39 @@ static int process_header(GString *buf, struct context *inc)
         * deal with unexpected or incorrect input data.
         */
 
+       /*
+        * Get up to the first 32 bytes of the file content. File format
+        * names end on SPACE or CTRL-Z (or NUL). Trim trailing SPACE
+        * before further processing.
+        */
        format_name = g_strndup(buf->str, 32);
+       p = strchr(format_name, CTRLZ);
+       if (p)
+               *p = '\0';
+       g_strchomp(format_name);
 
-       /* File format name ends on 0x20/0x1A, let's remove both. */
-       for (i = 1; i < 31; i++) {
-               if (format_name[i] == 0x1A) {
-                       format_name[i - 1] = 0;
-                       format_name[i] = 0;
-               }
-       }
-       g_strchomp(format_name); /* This is for additional padding spaces. */
-
-       format_name_sig = g_strndup(format_name, 5);
+       /*
+        * File format names either start with the "trace32" literal,
+        * or with a digit and SPACE.
+        */
+       format_name_sig = g_strndup(format_name, strlen(TRACE32));
+       has_trace32 = g_strcmp0(format_name_sig, TRACE32) == 0;
+       g_free(format_name_sig);
 
-       /* Desired file formats either start with digit+space or "trace32". */
-       if (g_strcmp0(format_name_sig, "trace32")) {
+       if (has_trace32) {
+               /* Literal "trace32" leader, binary header follows. */
                if (inc)
                        inc->format = AD_FORMAT_BINHDR;
-       } else if (g_ascii_isdigit(format_name[0]) && (format_name[1] == 0x20)) {
+       } else if (g_ascii_isdigit(format_name[0]) && (format_name[1] == SPACE)) {
+               /* Digit and SPACE leader, currently unsupported text header. */
                if (inc)
                        inc->format = AD_FORMAT_TXTHDR;
-               g_free(format_name_sig);
                g_free(format_name);
                if (inc)
                        sr_err("This format isn't implemented yet, aborting.");
                return SR_ERR;
        } else {
-               g_free(format_name_sig);
+               /* Unknown kind of format name. Unsupported. */
                g_free(format_name);
                if (inc)
                        sr_err("Don't know this file format, aborting.");
@@ -276,14 +287,12 @@ static int process_header(GString *buf, struct context *inc)
        }
 
        if (!device_id) {
-               g_free(format_name_sig);
                g_free(format_name);
                sr_err("Don't know how to handle this file with record size %d.",
                        record_size);
                return SR_ERR;
        }
 
-       g_free(format_name_sig);
        g_free(format_name);
 
        /* Stop processing the header if we just want to identify the file. */