Generate ZIP files the same way as Windows

libc/nexgen32e/zip.S

@@ -25,19 +25,17 @@
 	.hidden	__zip_start
 	.globl	__zip_start
 	.type	__zip_start,@object
-	.align	kZipCdirAlign
 __zip_start:
 	.previous/*
 	...
 	decentralized content
 	...
 	*/.section .zip.5,"",@progbits
-	.align	kZipCdirAlign
 __zip_end:
 	.long	kZipCdirHdrMagic	# magic
 	.short	0			# disk
 	.short	0			# starting disk
-	.short	v_zip_records		# records on disk
+	.short	v_zip_records		# number of records on disk
 	.short	v_zip_records		# records
 	.long	v_zip_cdirsize		# size of central directory
 	.long	RVA(__zip_start)	# central directory offset

libc/str/zipfindcentraldir.c

@@ -18,16 +18,34 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/zip.h"
 
-uint8_t *zipfindcentraldir(const uint8_t *map, size_t mapsize) {
-  const uint8_t *p, *pe;
-  for (p = map + mapsize - kZipCdirHdrMinSize,
-      pe = mapsize > 65536 + kZipCdirHdrMinSize
-               ? map + mapsize - 65536 - kZipCdirHdrMinSize
-               : map;
-       p >= pe; --p) {
-    if (ZIP_CDIR_MAGIC(p) == kZipCdirHdrMagic) {
-      return (/*unconst*/ uint8_t *)p;
-    }
+/**
+ * Locates End Of Central Directory record in ZIP file.
+ *
+ * We search backwards for the End Of Central Directory Record magnum.
+ * The ZIP spec says this can be anywhere in the last 64kb. We go all
+ * the way since .com.dbg binaries will have lots of DWARF stuff after
+ * the embedded .com binary. As such, we sanity check the other fields
+ * too to make sure the record seems legit and it's not just a random
+ * occurrence of the magnum.
+ *
+ * @param p points to file memory
+ * @param n is byte size of file
+ */
+uint8_t *zipfindcentraldir(const uint8_t *p, size_t n) {
+  size_t i;
+  if (n >= kZipCdirHdrMinSize) {
+    i = n - kZipCdirHdrMinSize;
+    do {
+      if (ZIP_CDIR_MAGIC(p + i) == kZipCdirHdrMagic &&
+          i + ZIP_CDIR_HDRSIZE(p + i) <= n &&
+          ZIP_CDIR_DISK(p + i) == ZIP_CDIR_STARTINGDISK(p + i) &&
+          ZIP_CDIR_RECORDSONDISK(p + i) == ZIP_CDIR_RECORDS(p + i) &&
+          ZIP_CDIR_RECORDS(p + i) * kZipCdirHdrMinSize <=
+              ZIP_CDIR_SIZE(p + i) &&
+          ZIP_CDIR_OFFSET(p + i) + ZIP_CDIR_SIZE(p + i) <= i) {
+        return (/*unconst*/ uint8_t *)(p + i);
+      }
+    } while (i--);
   }
   return NULL;
 }

libc/zip.h

@@ -10,7 +10,7 @@
 
 #define kZipAlign 2
 
-#define kZipCosmopolitanVersion 1
+#define kZipCosmopolitanVersion 20
 
 #define kZipOsDos         0
 #define kZipOsAmiga       1
@@ -45,7 +45,7 @@
 
 #define kZipCdirHdrMagic   0x06054b50 /* PK♣♠ "PK\5\6" */
 #define kZipCdirHdrMinSize 22
-#define kZipCdirAlign      64 /* our choice; actually 2 */
+#define kZipCdirAlign      kZipAlign
 #define kZipCdirHdrLinkableSize \
   ROUNDUP(kZipCfileHdrMinSize + PATH_MAX, kZipCdirAlign)
 

libc/zipos/find.c

@@ -29,6 +29,7 @@ ssize_t __zipos_find(struct Zipos *zipos, const struct ZiposUri *name) {
   for (i = 0, cf = ZIP_CDIR_OFFSET(zipos->cdir);
        i < ZIP_CDIR_RECORDS(zipos->cdir);
        ++i, cf += ZIP_CFILE_HDRSIZE(zipos->map + cf)) {
+    if (ZIP_CFILE_MAGIC(zipos->map + cf) != kZipCfileHdrMagic) DebugBreak();
     assert(ZIP_CFILE_MAGIC(zipos->map + cf) == kZipCfileHdrMagic);
     if (name->len == ZIP_CFILE_NAMESIZE(zipos->map + cf) &&
         memcmp(name->path, ZIP_CFILE_NAME(zipos->map + cf), name->len) == 0) {

libc/zipos/get.c

@@ -21,6 +21,7 @@
 #include "libc/calls/struct/stat.h"
 #include "libc/limits.h"
 #include "libc/runtime/runtime.h"
+#include "libc/str/str.h"
 #include "libc/sysv/consts/auxv.h"
 #include "libc/sysv/consts/map.h"
 #include "libc/sysv/consts/o.h"
@@ -36,9 +37,8 @@ struct Zipos *__zipos_get(void) {
   static bool once;
   const char *exe, *dir;
   char path[PATH_MAX];
-  size_t mapsize;
-  uint8_t *cdir;
-  void *map;
+  size_t size;
+  uint8_t *map, *base, *cdir;
   if (!once) {
     dir = nulltoempty(getenv("PWD")); /* suboptimal */
     exe = (const char *)getauxval(AT_EXECFN);
@@ -47,14 +47,23 @@ struct Zipos *__zipos_get(void) {
       exe = path;
     }
     if ((zipos.fd = open(exe, O_RDONLY)) != -1) {
-      if ((mapsize = getfiledescriptorsize(zipos.fd)) != SIZE_MAX &&
-          (map = mmap(NULL, mapsize, PROT_READ, MAP_SHARED, zipos.fd, 0)) !=
+      if ((size = getfiledescriptorsize(zipos.fd)) != SIZE_MAX &&
+          (map = mmap(NULL, size, PROT_READ, MAP_SHARED, zipos.fd, 0)) !=
               MAP_FAILED) {
-        if ((cdir = zipfindcentraldir(map, mapsize))) {
-          zipos.map = map;
+        if (endswith(exe, ".com.dbg")) {
+          if ((base = memmem(map, size, "MZqFpD", 6))) {
+            size -= base - map;
+          } else {
+            base = map;
+          }
+        } else {
+          base = map;
+        }
+        if ((cdir = zipfindcentraldir(base, size))) {
+          zipos.map = base;
           zipos.cdir = cdir;
         } else {
-          munmap(map, mapsize);
+          munmap(map, size);
         }
       }
     }