win32: code shrink has_exec_format()

In the code to detect binaries:

- use '|' rather than '+' to combine bytes;

- fix the test that the PE header is within the buffer;

- once we have the offset to the PE header make a pointer to it;

- cosmetic changes.

Saves 96 bytes.

1 files changed, 11 insertions, 13 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 82316e69d..1e3cce17a 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -414,8 +414,7 @@ mode_t mingw_umask(mode_t new_mode)
  */
 static int has_exec_format(const char *name)
 {
-        int n, sig;
-        unsigned int offset;
+        int n;
         unsigned char buf[1024];
 
         /* special case: skip DLLs, there are thousands of them! */
@@ -436,20 +435,19 @@ static int has_exec_format(const char *name)
          * the magic from the file command.
          */
         if (buf[0] == 'M' && buf[1] == 'Z') {
-                offset = (buf[0x19] << 8) + buf[0x18];
+                unsigned int offset = (buf[0x19] << 8) | buf[0x18];
                 if (offset > 0x3f) {
-                        offset = (buf[0x3f] << 24) + (buf[0x3e] << 16) +
-                                                (buf[0x3d] << 8) + buf[0x3c];
-                        if (offset < sizeof(buf)-100) {
-                                if (memcmp(buf+offset, "PE\0\0", 4) == 0) {
-                                        sig = (buf[offset+25] << 8) + buf[offset+24];
+                        offset = (buf[0x3f] << 24) | (buf[0x3e] << 16) |
+                                                (buf[0x3d] << 8) | buf[0x3c];
+                        if (offset + 100 < n) {
+                                unsigned char *ptr = buf + offset;
+                                if (memcmp(ptr, "PE\0\0", 4) == 0) {
+                                        unsigned int sig = (ptr[25] << 8) | ptr[24];
                                         if (sig == 0x10b || sig == 0x20b) {
-                                                sig = (buf[offset+23] << 8) + buf[offset+22];
-                                                if ((sig & 0x2000) != 0) {
-                                                        /* DLL */
+                                                sig = (ptr[23] << 8) | ptr[22];
+                                                if ((sig & 0x2000) != 0)        // DLL
                                                         return 0;
-                                                }
-                                                sig = buf[offset+92];
+                                                sig = ptr[92];
                                                 return (sig == 1 || sig == 2 || sig == 3 || sig == 7);
                                         }
                                 }