From a255cebc5794db96043be4349bca5060a83c8890 Mon Sep 17 00:00:00 2001
From: leitner <leitner>
Date: Mon, 2 Mar 2015 21:25:57 +0000
Subject: [PATCH]   mmap_read/mmap_shared on zero length files no longer fail
 but return a     zero length buffer

---
 CHANGES            | 2 ++
 mmap/mmap_read.c   | 9 ++++++---
 mmap/mmap_shared.c | 9 ++++++---
 mmap/mmap_unmap.c  | 2 +-
 4 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/CHANGES b/CHANGES
index d0f0b54..ccdce4d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -24,6 +24,8 @@
   add io_fd_flags so the caller can tell io_fd whether the socket is blocking
     (saves one fcntl syscall)
   more constness for stralloc and buffer
+  mmap_read/mmap_shared on zero length files no longer fail but return a
+    zero length buffer
 
 0.29:
   save 8 bytes in taia.h for 64-bit systems
diff --git a/mmap/mmap_read.c b/mmap/mmap_read.c
index 14dd6d9..7d9055f 100644
--- a/mmap/mmap_read.c
+++ b/mmap/mmap_read.c
@@ -30,9 +30,12 @@ extern const char* mmap_read(const char* filename,size_t * filesize) {
     register off_t o=lseek(fd,0,SEEK_END);
     if (sizeof(off_t)!=sizeof(size_t) && o > (off_t)(size_t)-1) { close(fd); return 0; }
     *filesize=(size_t)o;
-    map=mmap(0,*filesize,PROT_READ,MAP_SHARED,fd,0);
-    if (map==(char*)-1)
-      map=0;
+    if (o>0) {
+      map=mmap(0,*filesize,PROT_READ,MAP_SHARED,fd,0);
+      if (map==(char*)-1)
+	map=0;
+    } else
+      map="";
     close(fd);
     return map;
   }
diff --git a/mmap/mmap_shared.c b/mmap/mmap_shared.c
index d4c99ff..3064d7c 100644
--- a/mmap/mmap_shared.c
+++ b/mmap/mmap_shared.c
@@ -30,9 +30,12 @@ extern char* mmap_shared(const char* filename,size_t * filesize) {
     register off_t o=lseek(fd,0,SEEK_END);
     if (sizeof(off_t)!=sizeof(size_t) && o > (off_t)(size_t)-1) { close(fd); return 0; }
     *filesize=(size_t)o;
-    map=mmap(0,*filesize,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
-    if (map==(char*)-1)
-      map=0;
+    if (o) {
+      map=mmap(0,*filesize,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
+      if (map==(char*)-1)
+	map=0;
+    } else
+      map="";
     close(fd);
     return map;
   }
diff --git a/mmap/mmap_unmap.c b/mmap/mmap_unmap.c
index 994e486..ce8e419 100644
--- a/mmap/mmap_unmap.c
+++ b/mmap/mmap_unmap.c
@@ -13,6 +13,6 @@ int mmap_unmap(const char* mapped,size_t maplen) {
   (void)maplen;
   return UnmapViewOfFile(mapped)?0:-1;
 #else
-  return munmap((char*)mapped,maplen);
+  return maplen ? munmap((char*)mapped,maplen) : 0;
 #endif
 }