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Modified Common::Str to use exponential growth for its storage; also changed the meaning of 'capacity' from 'max length of string' to 'size of storage' (i.e. added one)

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svn-id: r34313
This commit is contained in:
Max Horn 2008-09-03 17:39:18 +00:00
parent e1918341af
commit c3d7c908e8
1 changed files with 10 additions and 11 deletions
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21
common/str.cpp
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@ -34,13 +34,12 @@ const String String::emptyString;
const char *String::emptyString = "";
#endif
static int computeCapacity(int len) {
static uint32 computeCapacity(uint32 len) {
// By default, for the capacity we use the nearest multiple of 32
// that leaves at least 16 chars of extra space (in case the string
// grows a bit).
// Finally, we subtract 1 to compensate for the trailing zero byte.
len += 16;
return ((len + 32 - 1) & ~0x1F) - 1;
return ((len + 32 - 1) & ~0x1F);
}
String::String(const char *str) : _size(0), _str(_storage) {
@ -73,7 +72,7 @@ void String::initWithCStr(const char *str, uint32 len) {
// Not enough internal storage, so allocate more
_extern._capacity = computeCapacity(len);
_extern._refCount = 0;
_str = (char *)malloc(_extern._capacity+1);
_str = (char *)malloc(_extern._capacity);
assert(_str != 0);
}
@ -86,7 +85,7 @@ String::String(const String &str)
: _size(str._size), _str(str.isStorageIntern() ? _storage : str._str) {
if (str.isStorageIntern()) {
// String in internal storage: just copy it
memcpy(_storage, str._storage, _builtinCapacity);
memcpy(_storage, str._storage, sizeof(_storage));
} else {
// String in external storage: use refcount mechanism
str.incRefCount();
@ -129,7 +128,7 @@ void String::ensureCapacity(uint32 new_size, bool keep_old) {
if (isStorageIntern()) {
isShared = false;
curCapacity = _builtinCapacity - 1;
curCapacity = _builtinCapacity;
} else {
isShared = (oldRefCount && *oldRefCount > 1);
curCapacity = _extern._capacity;
@ -140,24 +139,24 @@ void String::ensureCapacity(uint32 new_size, bool keep_old) {
if (!isShared && new_size <= curCapacity)
return;
if (isShared && new_size <= _builtinCapacity - 1) {
if (isShared && new_size < _builtinCapacity) {
// We share the storage, but there is enough internal storage: Use that.
newStorage = _storage;
newCapacity = _builtinCapacity - 1;
newCapacity = _builtinCapacity;
} else {
// We need to allocate storage on the heap!
// Compute a suitable new capacity limit
newCapacity = computeCapacity(new_size);
newCapacity = MAX(curCapacity * 2, computeCapacity(new_size));
// Allocate new storage
newStorage = (char *)malloc(newCapacity+1);
newStorage = (char *)malloc(newCapacity);
assert(newStorage);
}
// Copy old data if needed, elsewise reset the new storage.
if (keep_old) {
assert(_size <= newCapacity);
assert(_size < newCapacity);
memcpy(newStorage, _str, _size + 1);
} else {
_size = 0;