Subject: Abi string class
From: Mike Nordell (tamlin@algonet.se)
Date: Thu Feb 01 2001 - 00:50:44 CST
Well, I've now taken the few hours it took to assemble something that at
least resembles a string class to use in AbiWord.
Why?
None of the existing string classes I've seen are fit for use in AW.
std::string is a no-no since it's using templates, exceptions and the world
is still full of bad implementations. For us to have a string class it need
to match at least the following criteria:
- Be completely portable. That means only ANSI C and a small subset of C++.
- Not use new/delete since we don't allow exceptions.
- Not use new(std::nothrow) since ancient libraries don't support it.
- Not use the bool type, portability.
and some others that get lost with these major design restrictions.
This class is currently a very light wrapper around a plain char*, but I
have tried to make it as efficient and exception safe as possible.
Unfortunately there's a tradeof between semantics/syntax of its use, and a
completely "safe" implementation. We want to be able to write
UT_String s1("foo");
or
s1 = "bar";
but to do this we would have to use exceptions to be "safe". Since we can't
use exceptions this implementation is "somewhat" unsafe (it keeps a safe
internal state, but in case of out-of-memory conditions it keeps its old
value). To fix this we would have to forbid anything but the default
constructor, and we would have to write assignment as
if (!s1.assign("bar"))
I traded safety for readability. If this turns out to be an issue of
controversy I'll do it the "safe" way, but it would hurt readability much
IMO.
I also have some ideas of an XML_Char class if this one turns out to be
useful. Such a class could replace more than a few wasteful static buffers
we currently have that most of the time aren't even half-full.
I've written test cases, and it passes all of'em. But, I'd like your input
on the interface.
class UT_String
{
public:
#ifdef UT_STRING_FOR_ABIWORD
typedef UT_Bool UT_Str_Bool;
#else
typedef bool UT_Str_Bool;
#endif
UT_String();
UT_String(const char* sz);
UT_String(const UT_String& rhs);
~UT_String();
UT_String& operator=(const UT_String& rhs);
UT_String& operator=(const char* rhs);
UT_String& operator+=(const UT_String& rhs);
UT_String& operator+=(const char* rhs);
size_t size() const;
UT_Str_Bool empty() const;
UT_Str_Bool operator==(const UT_String& rhs) const;
UT_Str_Bool operator==(const char* rhs) const;
// The returned pointer is only valid until the
// next UT_String non-const operation.
const char* c_str() const;
private:
class UT_StringImpl* pimpl;
};
Comments, ideas or criticism?
/Mike
P.S.
Wether accepted as-is or with changes, I plan to post the class with its
test cases for other platforms to rey before committing anything.
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