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os/vfs.h: don't truncate File_content

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The 'File_content' utility throws an exception whenever a file happens
to get truncated during the reading process. But it silently truncates
the data against the specified limit. In practice, exceeding the limit
is usually an error case. This patch enhances the 'File_content' utility
by throwing 'Truncated_during_read' in the limit-exceeded case as well,
in order to ease the diagnosis of such cases.

Issue #4788
This commit is contained in:
Norman Feske 2023-03-15 15:33:07 +01:00
parent 40333a8ee2
commit fd7001d020
1 changed files with 13 additions and 3 deletions
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16
repos/os/include/os/vfs.h
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@ -574,6 +574,10 @@ void Genode::with_xml_file_content(Readonly_file const &file,
class Genode::File_content
{
public:
struct Limit { size_t value; };
private:
class Buffer
@ -597,6 +601,14 @@ class Genode::File_content
} _buffer;
static size_t _checked_file_size(Vfs::file_size file_size, Limit limit)
{
if (file_size <= limit.value)
return size_t(file_size);
throw Truncated_during_read();
}
public:
typedef Directory::Nonexistent_file Nonexistent_file;
@ -604,8 +616,6 @@ class Genode::File_content
typedef Directory::Path Path;
struct Limit { size_t value; };
/**
* Constructor
*
@ -616,7 +626,7 @@ class Genode::File_content
File_content(Allocator &alloc, Directory const &dir, Path const &rel_path,
Limit limit)
:
_buffer(alloc, min((size_t)dir.file_size(rel_path), limit.value))
_buffer(alloc, _checked_file_size(dir.file_size(rel_path), limit))
{
/* read the file content into the buffer */
with_raw_file_content(Readonly_file(dir, rel_path),