Added debug output to sendfile

src/sendfile.c

@@ -1,8 +1,10 @@
+#include <unistd.h>
 
 #include "util.h"
 #include "desock.h"
 #include "syscall.h"
 #include "musl-features.h"
+#include "hooks.h"
 
 VISIBLE
 ssize_t sendfile (int out_fd, int in_fd, off_t* ofs, size_t count) {
@@ -11,6 +13,44 @@ ssize_t sendfile (int out_fd, int in_fd, off_t* ofs, size_t count) {
     }
 
     DEBUG_LOG("sendfile(%d, %d, %p, %lu) = %lu", out_fd, in_fd, ofs, count, count);
+
+#ifdef DEBUG
+    off_t old_offset = 0;
+    size_t consumed = 0;
+    char buf[512];
+
+    if (ofs) {
+        old_offset = lseek(in_fd, 0, SEEK_CUR);
+
+        if (old_offset < 0) {
+            _error("Cannot lseek() in sendfile() in_fd");
+        }
+
+        if (lseek(in_fd, *ofs, SEEK_SET) < 0) {
+            _error("Invalid ofs in sendfile()");
+        }
+    }
+
+    while (consumed < count) {
+        size_t delta = count - consumed;
+        ssize_t r = syscall_cp(SYS_read, in_fd, buf, MIN(sizeof(buf), delta));
+
+        if (r < 0) {
+            _error("Cannot read from file in sendfile()");
+        }
+
+        hook_output(buf, (size_t) r);
+
+        consumed += (size_t) r;
+    }
+
+    if (ofs) {
+        if (lseek(in_fd, old_offset, SEEK_SET) < 0) {
+            _error("Cannot restore file offset in sendfile()");
+        }
+    }
+#endif
+
     return count;
 }
 VERSION(sendfile)