MappedFile and FileMap should support zero-length mappings.

Bug: http://b/119818070 "app crashes when reading asset of zero length"
Test: ran tests
Change-Id: Idd2ad6f6e72c8e445aff78a460fac96dea41c950

1 files changed, 14 insertions, 19 deletions

diff --git a/libutils/FileMap.cpp b/libutils/FileMap.cpp
index 5feb2aa76..1202c156d 100644
--- a/libutils/FileMap.cpp
+++ b/libutils/FileMap.cpp
@@ -174,12 +174,6 @@ bool FileMap::create(const char* origFileName, int fd, off64_t offset, size_t le
         return false;
     }
 #else // !defined(__MINGW32__)
-    int     prot, flags, adjust;
-    off64_t adjOffset;
-    size_t  adjLength;
-
-    void* ptr;
-
     assert(fd >= 0);
     assert(offset >= 0);
     assert(length > 0);
@@ -193,20 +187,23 @@ bool FileMap::create(const char* origFileName, int fd, off64_t offset, size_t le
         }
     }
 
-    adjust = offset % mPageSize;
-    adjOffset = offset - adjust;
-    adjLength = length + adjust;
+    int adjust = offset % mPageSize;
+    off64_t adjOffset = offset - adjust;
+    size_t adjLength = length + adjust;
 
-    flags = MAP_SHARED;
-    prot = PROT_READ;
-    if (!readOnly)
-        prot |= PROT_WRITE;
+    int flags = MAP_SHARED;
+    int prot = PROT_READ;
+    if (!readOnly) prot |= PROT_WRITE;
 
-    ptr = mmap(nullptr, adjLength, prot, flags, fd, adjOffset);
+    void* ptr = mmap(nullptr, adjLength, prot, flags, fd, adjOffset);
     if (ptr == MAP_FAILED) {
-        ALOGE("mmap(%lld,%zu) failed: %s\n",
-            (long long)adjOffset, adjLength, strerror(errno));
-        return false;
+        if (errno == EINVAL && length == 0) {
+            ptr = nullptr;
+            adjust = 0;
+        } else {
+            ALOGE("mmap(%lld,%zu) failed: %s\n", (long long)adjOffset, adjLength, strerror(errno));
+            return false;
+        }
     }
     mBasePtr = ptr;
 #endif // !defined(__MINGW32__)
@@ -217,8 +214,6 @@ bool FileMap::create(const char* origFileName, int fd, off64_t offset, size_t le
     mDataPtr = (char*) mBasePtr + adjust;
     mDataLength = length;
 
-    assert(mBasePtr != NULL);
-
     ALOGV("MAP: base %p/%zu data %p/%zu\n",
         mBasePtr, mBaseLength, mDataPtr, mDataLength);