file abstraction: actually follow lseek semantics

Signed-off-by: Tianhao Chai <cth451@aosc.io>
(cherry picked from commit 0b60970d5a)

akode/lib/file.h

@@ -76,7 +76,7 @@ public:
     * Seeks to the position.
     * Behaves semantically as lseek.
     */
-    virtual bool seek(long to, int whence = SEEK_SET) = 0;
+    virtual ssize_t seek(long to, int whence = SEEK_SET) = 0;
    /*!
     * Returns current position in file, or negative if unknown.
     */

akode/lib/localfile.cpp

@@ -115,11 +115,11 @@ long LocalFile::write(const char* ptr, long num) {
     return n;
 }
 
-bool LocalFile::seek(long to, int whence) {
-    if(_fd == -1) return false;
-    int s = ::lseek(_fd, to, whence);
+ssize_t LocalFile::seek(long to, int whence) {
+    if(_fd == -1) return -1;
+    ssize_t s = ::lseek(_fd, to, whence);
     if (s >= 0) pos = s;
-    return (s >= 0);
+    return s;
 }
 
 long LocalFile::position() const {

akode/lib/localfile.h

@@ -50,7 +50,7 @@ public:
     long read(char* ptr, long num);
     long write(const char* ptr, long num);
 
-    bool seek(long to, int whence = SEEK_SET);
+    ssize_t seek(long to, int whence = SEEK_SET);
     long position() const;
     long length() const;
 

akode/lib/mmapfile.cpp

@@ -94,7 +94,7 @@ long MMapFile::write(const char*, long) {
     return false;
 }
 
-bool MMapFile::seek(long to, int whence) {
+ssize_t MMapFile::seek(long to, int whence) {
     if(!handle) return false;
 
     long newpos = 0;
@@ -109,12 +109,12 @@ bool MMapFile::seek(long to, int whence) {
             newpos = len + to;
             break;
         default:
-            return false;
+            return length();
     }
     if (newpos > len || newpos < 0)
-        return false;
+        return -1;
     pos = newpos;
-    return true;
+    return newpos;
 }
 
 long MMapFile::position() const {

akode/lib/mmapfile.h

@@ -47,7 +47,7 @@ public:
     long read(char* ptr, long num);
     long write(const char*, long);
 
-    bool seek(long to, int whence = SEEK_SET);
+    ssize_t seek(long to, int whence = SEEK_SET);
     long position() const;
     long length() const;