Implement zip file streaming

[cemeyer]

When searching large zip files (e.g. multi-GB logs or something), it's desirable not to decompress the whole thing in memory at one time. Instead, a psuedo-FILE object can be created with fopencookie(3) (glibc) or funopen(3) (BSD) that only needs to seek forwards and decompress small chunks at a time, and that FILE* can be passed to the ordinary streaming search routine.

Here's an example of what fopencookie/funopen-wrapped zip streaming looks like: https://github.com/cemeyer/Zlib-FILE (that implementation is permissively licensed, feel free to just drop it in to the_silver_searcher).

Aside from the FILE-wrapper code, the actual patch should be fairly small. Something like this:

--- a/src/search.c
+++ b/src/search.c
@@ -315,14 +315,10 @@ void search_file(const char *file_full_path) {
     if (opts.search_zip_files) {
         ag_compression_type zip_type = is_zipped(buf, f_len);
         if (zip_type != AG_NO_COMPRESSION) {
-            int _buf_len = (int)f_len;
-            char *_buf = decompress(zip_type, buf, f_len, file_full_path, &_buf_len);
-            if (_buf == NULL || _buf_len == 0) {
-                log_err("Cannot decompress zipped file %s", file_full_path);
-                goto cleanup;
-            }
-            search_buf(_buf, _buf_len, file_full_path);
-            free(_buf);
+           log_debug("%s is a zip file. stream searching", file_full_path);
+           fp = decompress_file(zip_type, ...);
+           search_stream(fp, file_full_path);
+           fclose(fp);
             goto cleanup;
         }
     }

[cemeyer]

See #1106.