AP_ROMFS: remove requirement that returned buffer is null-terminated

Also take the opportunity to clarify the function descriptions.

Tools/ardupilotwaf/embed.py

@@ -32,21 +32,14 @@ def embed_file(out, f, idx, embedded_name, uncompressed):
     write_encode(out, '__EXTFLASHFUNC__ static const uint8_t ap_romfs_%u[] = {' % idx)
 
     if uncompressed:
-        # terminate if there's not already an existing null. we don't add it to
-        # the contents to avoid storing the wrong length
-        null_terminate = 0 not in contents
         b = contents
     else:
         # compress it (max level, max window size, raw stream, max mem usage)
         z = zlib.compressobj(level=9, method=zlib.DEFLATED, wbits=-15, memLevel=9)
         b = z.compress(contents)
         b += z.flush()
-        # decompressed data will be null terminated at runtime, nothing to do here
-        null_terminate = False
 
     write_encode(out, ",".join(str(c) for c in b))
-    if null_terminate:
-        write_encode(out, ",0")
     write_encode(out, '};\n\n');
     return crc, len(contents)
 

libraries/AP_ROMFS/AP_ROMFS.cpp

@@ -45,10 +45,8 @@ const AP_ROMFS::embedded_file *AP_ROMFS::find_file(const char *name)
 }
 
 /*
-  find a compressed file and uncompress it. Space for decompressed data comes
-  from malloc. Caller must be careful to free the resulting data after use. The
-  file data buffer is guaranteed to contain at least one null (though it may be
-  at buf[size]).
+  Find the named file and return its decompressed data and size. Caller must
+  call AP_ROMFS::free() on the return value after use to free it.
 */
 const uint8_t *AP_ROMFS::find_decompress(const char *name, uint32_t &size)
 {
@@ -61,14 +59,11 @@ const uint8_t *AP_ROMFS::find_decompress(const char *name, uint32_t &size)
     size = f->decompressed_size;
     return f->contents;
 #else
-    uint8_t *decompressed_data = (uint8_t *)malloc(f->decompressed_size+1);
+    uint8_t *decompressed_data = (uint8_t *)malloc(f->decompressed_size);
     if (!decompressed_data) {
         return nullptr;
     }
 
-    // explicitly null-terminate the data
-    decompressed_data[f->decompressed_size] = 0;
-
     TINF_DATA *d = (TINF_DATA *)malloc(sizeof(TINF_DATA));
     if (!d) {
         ::free(decompressed_data);
@@ -100,7 +95,7 @@ const uint8_t *AP_ROMFS::find_decompress(const char *name, uint32_t &size)
 #endif
 }
 
-// free returned data
+// free decompressed file data
 void AP_ROMFS::free(const uint8_t *data)
 {
 #ifndef HAL_ROMFS_UNCOMPRESSED

libraries/AP_ROMFS/AP_ROMFS.h

@@ -7,13 +7,11 @@
 
 class AP_ROMFS {
 public:
-    // find a file and de-compress, assumning gzip format. The
-    // decompressed data will be allocated with malloc(). You must
-    // call AP_ROMFS::free() on the return value after use. The next byte after
-    // the file data is guaranteed to be null.
+    // Find the named file and return its decompressed data and size. Caller
+    // must call AP_ROMFS::free() on the return value after use to free it.
     static const uint8_t *find_decompress(const char *name, uint32_t &size);
 
-    // free returned data
+    // free decompressed file data
     static void free(const uint8_t *data);
 
     /*