AP_ROMFS: added support for compressed files in ROMFS

libraries/AP_ROMFS/AP_ROMFS.cpp

@@ -17,6 +17,7 @@
  */
 
 #include "AP_ROMFS.h"
+#include "tinf.h"
 
 #ifdef HAL_HAVE_AP_ROMFS_EMBEDDED_H
 #include <ap_romfs_embedded.h>
@@ -37,3 +38,61 @@ const uint8_t *AP_ROMFS::find_file(const char *name, uint32_t &size)
     }
     return nullptr;
 }
+
+/*
+  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.
+*/
+uint8_t *AP_ROMFS::find_decompress(const char *name, uint32_t &size)
+{
+    uint32_t compressed_size;
+    const uint8_t *compressed_data = find_file(name, compressed_size);
+    if (!compressed_data) {
+        return nullptr;
+    }
+
+    // last 4 bytes of gzip file are length of decompressed data
+    const uint8_t *p = &compressed_data[compressed_size-4];
+    uint32_t decompressed_size = p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
+    
+    uint8_t *decompressed_data = (uint8_t *)malloc(decompressed_size);
+    if (!decompressed_data) {
+        return nullptr;
+    }
+
+    TINF_DATA *d = (TINF_DATA *)malloc(sizeof(TINF_DATA));
+    if (!d) {
+        free(decompressed_data);
+        return nullptr;
+    }
+    uzlib_uncompress_init(d, NULL, 0);
+
+    d->source = compressed_data;
+    d->source_limit = compressed_data + compressed_size - 4;
+
+    // assume gzip format
+    int res = uzlib_gzip_parse_header(d);
+    if (res != TINF_OK) {
+        free(decompressed_data);
+        free(d);
+        return nullptr;
+    }
+
+    d->dest = decompressed_data;
+    d->destSize = decompressed_size;
+
+    // we don't check CRC, as it just wastes flash space for constant
+    // ROMFS data
+    res = uzlib_uncompress(d);
+
+    free(d);
+    
+    if (res != TINF_OK) {
+        free(decompressed_data);
+        return nullptr;
+    }
+
+    size = decompressed_size;
+    return decompressed_data;
+}