PNGLoader: Use MappedFile.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/c0009e3173d

AK/MappedFile.cpp

@@ -5,25 +5,29 @@
 #include <unistd.h>
 #include <stdio.h>
 
+//#define DEBUG_MAPPED_FILE
+
 namespace AK {
 
 MappedFile::MappedFile(const String& file_name)
     : m_file_name(file_name)
 {
-    m_file_length = PAGE_SIZE;
+    m_size = PAGE_SIZE;
     m_fd = open(m_file_name.characters(), O_RDONLY);
     
     if (m_fd != -1) {
         struct stat st;
         fstat(m_fd, &st);
-        m_file_length = st.st_size;
-        m_map = mmap(nullptr, m_file_length, PROT_READ, MAP_SHARED, m_fd, 0);
+        m_size = st.st_size;
+        m_map = mmap(nullptr, m_size, PROT_READ, MAP_SHARED, m_fd, 0);
 
         if (m_map == MAP_FAILED)
             perror("");
     }
 
-    dbgprintf("MappedFile{%s} := { m_fd=%d, m_file_length=%zu, m_map=%p }\n", m_file_name.characters(), m_fd, m_file_length, m_map);
+#ifdef DEBUG_MAPPED_FILE
+    dbgprintf("MappedFile{%s} := { m_fd=%d, m_size=%u, m_map=%p }\n", m_file_name.characters(), m_fd, m_size, m_map);
+#endif
 }
 
 MappedFile::~MappedFile()
@@ -36,21 +40,23 @@ void MappedFile::unmap()
     if (!is_valid())
         return;
     ASSERT(m_fd != -1);
-    int rc = munmap(m_map, m_file_length);
+    int rc = munmap(m_map, m_size);
+    ASSERT(rc == 0);
+    rc = close(m_fd);
     ASSERT(rc == 0);
     m_file_name = { };
-    m_file_length = 0;
+    m_size = 0;
     m_fd = -1;
     m_map = (void*)-1;
 }
 
 MappedFile::MappedFile(MappedFile&& other)
     : m_file_name(move(other.m_file_name))
-    , m_file_length(other.m_file_length)
+    , m_size(other.m_size)
     , m_fd(other.m_fd)
     , m_map(other.m_map)
 {
-    other.m_file_length = 0;
+    other.m_size = 0;
     other.m_fd = -1;
     other.m_map = (void*)-1;
 }
@@ -61,7 +67,7 @@ MappedFile& MappedFile::operator=(MappedFile&& other)
         return *this;
     unmap();
     swap(m_file_name, other.m_file_name);
-    swap(m_file_length, other.m_file_length);
+    swap(m_size, other.m_size);
     swap(m_fd, other.m_fd);
     swap(m_map, other.m_map);
     return *this;

AK/MappedFile.h

@@ -18,11 +18,11 @@ public:
 
     void* pointer() { return m_map; }
     const void* pointer() const { return m_map; }
-    size_t file_length() const { return m_file_length; }
+    size_t size() const { return m_size; }
 
 private:
     String m_file_name;
-    size_t m_file_length { 0 };
+    size_t m_size { 0 };
     int m_fd { -1 };
     void* m_map { (void*)-1 };
 };

SharedGraphics/PNGLoader.cpp

@@ -1,5 +1,6 @@
 #include <SharedGraphics/PNGLoader.h>
 #include <AK/NetworkOrdered.h>
+#include <AK/MappedFile.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ -101,42 +102,10 @@ static bool process_chunk(Streamer&, PNGLoadingContext& context);
 
 RetainPtr<GraphicsBitmap> load_png(const String& path)
 {
-    int fd = open(path.characters(), O_RDONLY);
-    if (fd < 0) {
-        perror("open");
+    MappedFile mapped_file(path);
+    if (!mapped_file.is_valid())
         return nullptr;
-    }
-
-    struct stat st;
-    if (fstat(fd, &st) < 0) {
-        perror("fstat");
-        if (close(fd) < 0)
-            perror("close");
-        return nullptr;
-    }
-
-    if (st.st_size < 8) {
-        if (close(fd) < 0)
-            perror("close");
-        return nullptr;
-    }
-
-    auto* mapped_file = (byte*)mmap(nullptr, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
-    if (mapped_file == MAP_FAILED) {
-        if (close(fd) < 0)
-            perror("close");
-        return nullptr;
-    }
-
-    auto bitmap = load_png_impl(mapped_file, st.st_size);
-
-    if (munmap(mapped_file, st.st_size) < 0)
-        perror("munmap");
-
-    if (close(fd) < 0)
-        perror("close");
-
-    return bitmap;
+    return load_png_impl((const byte*)mapped_file.pointer(), mapped_file.size());
 }
 
 [[gnu::always_inline]] static inline byte paeth_predictor(int a, int b, int c)