Fix compression implementation and reduce benchmark timeouts

- Revert streaming compression to non-streaming approach (fixes decompression errors)
- Reduce client timeout in benchmark from 600s to 60s
- Simplify wait time calculation in benchmark to fixed 2s

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

benchmark_network.sh

@@ -233,19 +233,14 @@ run_fastsync() {
     local output
     local compress_flag=""
     [ "$use_compress" -eq 0 ] && compress_flag="-c"
-    output=$(timeout 600 "$CLIENT_BIN" -h "$HOST" -p "$port" -s "$SRC_DIR" -n "$nconn" $compress_flag 2>&1) || true
+    output=$(timeout 60 "$CLIENT_BIN" -h "$HOST" -p "$port" -s "$SRC_DIR" -n "$nconn" $compress_flag 2>&1) || true
     
     # Extract actual transfer time from client output
     local transfer_ms=$(echo "$output" | grep -oP 'ms=\K[0-9.]+' || echo "0")
     local transfer_ms_int=$(echo "$transfer_ms" | awk '{printf "%d", $1+0}')
     
-    # Aggressive wait times for quick progress checks
-    # Formula: max(transfer_time/1000 + 1s, 1s) + 1s extra for 1 conn
-    local wait_time=$(( transfer_ms_int / 1000 + 1 ))
-    [ "$nconn" -eq 1 ] && wait_time=$(( wait_time + 1 ))
-    [ "$wait_time" -lt 1 ] && wait_time=1
-    
-    sleep $wait_time
+    # Use fixed short wait time since timeout already limits client
+    sleep 2
     kill "$spid" 2>/dev/null || true
     wait "$spid" 2>/dev/null || true
     sync

src/client.c

@@ -606,21 +606,32 @@ static int send_batch_files(sync_ctx_t *ctx, file_task_t **tasks, int count) {
             }
             
             int compressed_size = LZ4_compress_default(file_buf, comp_buf, stats[i].st_size, max_compressed);
+            free(file_buf);
+            
             if (compressed_size > 0 && (uint64_t)compressed_size < (uint64_t)stats[i].st_size) {
                 // Compression succeeded and reduced size
                 meta.compress = COMPRESS_LZ4;
                 meta.compressed_size = compressed_size;
                 data_to_send = comp_buf;
                 data_size = compressed_size;
-                free(file_buf);
             } else {
-                // Compression failed or didn't reduce size, send uncompressed
+                // Compression didn't reduce size, send uncompressed
                 free(comp_buf);
-                data_to_send = file_buf;
-                data_size = stats[i].st_size;
+                data_to_send = NULL; // Will use sendfile below
             }
-        } else {
-            // No compression: use sendfile() for zero-copy transfer
+        }
+        
+        // If data_to_send is NULL (compression not beneficial or not requested), use sendfile
+        if (!data_to_send) {
+            meta.compress = COMPRESS_NONE;
+            meta.compressed_size = 0;
+            if (lseek(fds[i], 0, SEEK_SET) < 0) {
+                perror("lseek for sendfile");
+                for (int j = 0; j < count; j++) close(fds[j]);
+                free(fds); free(stats);
+                return -1;
+            }
+            
             // Send metadata first
             if (writen(ctx->tcp_fd, &meta, sizeof(meta)) != sizeof(meta)) {
                 for (int j = 0; j < count; j++) close(fds[j]);
@@ -652,7 +663,7 @@ static int send_batch_files(sync_ctx_t *ctx, file_task_t **tasks, int count) {
             printf("[thread] Sent (pipelined+sendfile): %s\n", tasks[i]->rel_path);
             continue;  // Skip to next file
         }
-
+        
         // Send metadata for compressed file
         if (writen(ctx->tcp_fd, &meta, sizeof(meta)) != sizeof(meta)) {
             free(data_to_send);
@@ -667,7 +678,7 @@ static int send_batch_files(sync_ctx_t *ctx, file_task_t **tasks, int count) {
             return -1;
         }
 
-        // Send data (compressed or uncompressed)
+        // Send compressed data
         if (writen(ctx->tcp_fd, data_to_send, data_size) != (ssize_t)data_size) {
             free(data_to_send);
             for (int j = 0; j < count; j++) close(fds[j]);