From 1a6331551a025ddcc1772ae447c326ec70e0e107 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 4 Nov 2012 22:44:05 +0200
Subject: [PATCH] Add a dedicated exception class for a bad seek operation

---
 source/io/memory.cpp   |  2 +-
 source/io/seekable.cpp | 18 ++++++++++++++++--
 source/io/seekable.h   |  9 +++++++++
 3 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/source/io/memory.cpp b/source/io/memory.cpp
index f64b4be..37954cc 100644
--- a/source/io/memory.cpp
+++ b/source/io/memory.cpp
@@ -116,7 +116,7 @@ SeekOffset Memory::seek(SeekOffset off, SeekType type)
 		throw invalid_argument("Memory::seek");
 
 	if(new_pos<begin || new_pos>end)
-		throw out_of_range("Memory::seek");
+		throw bad_seek(off, type);
 
 	pos = new_pos;
 	eof_flag = false;
diff --git a/source/io/seekable.cpp b/source/io/seekable.cpp
index 0c3b0b9..a75cf33 100644
--- a/source/io/seekable.cpp
+++ b/source/io/seekable.cpp
@@ -1,11 +1,12 @@
 #ifndef WIN32
 #define _LARGEFILE64_SOURCE
+#include <cerrno>
 #include <unistd.h>
 #else
 #include <windows.h>
 #endif
-#include <stdexcept>
 #include <msp/core/systemerror.h>
+#include <msp/strings/format.h>
 #include "handle.h"
 #include "handle_private.h"
 #include "seekable.h"
@@ -43,6 +44,14 @@ int sys_seek_type(SeekType st)
 namespace Msp {
 namespace IO {
 
+bad_seek::bad_seek(SeekOffset offset, SeekType type):
+	runtime_error(type==S_BEG ? lexical_cast(offset) :
+		type==S_CUR ? format("CUR%+d", offset) :
+		type==S_END ? format("END%+d", offset) :
+		format("SeekType(%d)", type))
+{ }
+
+
 SeekOffset sys_seek(Handle &handle, SeekOffset offset, SeekType type)
 {
 #ifdef WIN32
@@ -59,7 +68,12 @@ SeekOffset sys_seek(Handle &handle, SeekOffset offset, SeekType type)
 #else
 	off64_t ret = lseek64(*handle, offset, sys_seek_type(type));
 	if(ret==(off64_t)-1)
-		throw system_error("lseek64");
+	{
+		if(errno==EINVAL)
+			throw bad_seek(offset, type);
+		else
+			throw system_error("lseek64");
+	}
 
 	return ret;
 #endif
diff --git a/source/io/seekable.h b/source/io/seekable.h
index 1fc3f89..f0170b4 100644
--- a/source/io/seekable.h
+++ b/source/io/seekable.h
@@ -1,6 +1,7 @@
 #ifndef MSP_IO_SEEKABLE_H_
 #define MSP_IO_SEEKABLE_H_
 
+#include <stdexcept>
 #include <msp/core/inttypes.h>
 #include "base.h"
 
@@ -19,6 +20,14 @@ enum SeekType
 };
 
 
+class bad_seek: public std::runtime_error
+{
+public:
+	bad_seek(SeekOffset, SeekType);
+	virtual ~bad_seek() throw() { }
+};
+
+
 class Seekable: public Base
 {
 protected:
-- 
2.43.0