Bug 394425 - nsCacheMetaData: alloc key & value & metadata in one malloc call

r+sr=shaver
This commit is contained in:
Alfred Kayser 2009-09-16 17:56:09 +02:00
parent b361f3d1e5
commit 4596769de6
2 changed files with 92 additions and 158 deletions

View File

@ -40,38 +40,22 @@
#include "nsCacheMetaData.h"
#include "nsICacheEntryDescriptor.h"
#include "nsString.h"
#include "nsReadableUtils.h"
#include "plstr.h"
nsCacheMetaData::nsCacheMetaData()
: mData(nsnull), mMetaSize(0)
{
}
void
nsCacheMetaData::Clear()
{
mMetaSize = 0;
MetaElement * elem;
while (mData) {
elem = mData->mNext;
delete mData;
mData = elem;
}
}
#include "prmem.h"
const char *
nsCacheMetaData::GetElement(const char * key)
{
// We assume the number of meta data elements will be very small, so
// we keep it real simple. Singly-linked list, linearly searched.
const char * data = mBuffer;
const char * limit = mBuffer + mMetaSize;
MetaElement * elem = mData;
while (elem) {
if (elem->mKey.EqualsASCII(key))
return elem->mValue;
elem = elem->mNext;
while (data < limit) {
// Point to the value part
const char * value = data + strlen(data) + 1;
if (strcmp(data, key) == 0)
return value;
// Skip value part
data = value + strlen(value) + 1;
}
return nsnull;
}
@ -81,55 +65,53 @@ nsresult
nsCacheMetaData::SetElement(const char * key,
const char * value)
{
PRUint32 keySize = strlen(key);
PRUint32 valueSize = value ? strlen(value) : 0;
const PRUint32 keySize = strlen(key) + 1;
char * pos = (char *)GetElement(key);
// find and remove or update old meta data element
MetaElement * elem = mData, * last = nsnull;
while (elem) {
if (elem->mKey.Equals(key)) {
// Get length of old value
PRUint32 oldValueLen = strlen(elem->mValue);
if (valueSize == oldValueLen) {
// Just replace value
memcpy(elem->mValue, value, valueSize);
return NS_OK;
}
// remove elem
if (last)
last->mNext = elem->mNext;
else
mData = elem->mNext;
// 2 for the zero bytes of both strings
mMetaSize -= 2 + keySize + oldValueLen;
delete elem;
break;
if (!value) {
// No value means remove the key/value pair completely, if existing
if (pos) {
PRUint32 oldValueSize = strlen(pos) + 1;
PRUint32 offset = pos - mBuffer;
PRUint32 remainder = mMetaSize - (offset + oldValueSize);
memmove(pos - keySize, pos + oldValueSize, remainder);
mMetaSize -= keySize + oldValueSize;
}
last = elem;
elem = elem->mNext;
return NS_OK;
}
// allocate new meta data element
if (value) {
elem = new (value, valueSize) MetaElement;
if (!elem)
return NS_ERROR_OUT_OF_MEMORY;
elem->mKey.Assign(key);
const PRUint32 valueSize = strlen(value) + 1;
PRUint32 newSize = mMetaSize + valueSize;
if (pos) {
const PRUint32 oldValueSize = strlen(pos) + 1;
const PRUint32 offset = pos - mBuffer;
const PRUint32 remainder = mMetaSize - (offset + oldValueSize);
// insert after last or as first element...
if (last) {
elem->mNext = last->mNext;
last->mNext = elem;
}
else {
elem->mNext = mData;
mData = elem;
}
// Update the value in place
newSize -= oldValueSize;
nsresult rv = EnsureBuffer(newSize);
NS_ENSURE_SUCCESS(rv, rv);
// Adjust CacheMetaData size, 2 for the zero bytes of both strings
mMetaSize += 2 + keySize + valueSize;
// Move the remainder to the right place
pos = mBuffer + offset;
memmove(pos + valueSize, pos + oldValueSize, remainder);
} else {
// allocate new meta data element
newSize += keySize;
nsresult rv = EnsureBuffer(newSize);
NS_ENSURE_SUCCESS(rv, rv);
// Add after last element
pos = mBuffer + mMetaSize;
memcpy(pos, key, keySize);
pos += keySize;
}
// Update value
memcpy(pos, value, valueSize);
mMetaSize = newSize;
return NS_OK;
}
@ -141,56 +123,19 @@ nsCacheMetaData::FlattenMetaData(char * buffer, PRUint32 bufSize)
return NS_ERROR_OUT_OF_MEMORY;
}
MetaElement * elem = mData;
while (elem) {
PRUint32 keySize = 1 + elem->mKey.Length();
memcpy(buffer, elem->mKey.get(), keySize);
buffer += keySize;
PRUint32 valSize = 1 + strlen(elem->mValue);
memcpy(buffer, elem->mValue, valSize);
buffer += valSize;
elem = elem->mNext;
}
memcpy(buffer, mBuffer, mMetaSize);
return NS_OK;
}
nsresult
nsCacheMetaData::UnflattenMetaData(const char * data, PRUint32 size)
{
if (size == 0) return NS_OK;
if (data && size) {
nsresult rv = EnsureBuffer(size);
NS_ENSURE_SUCCESS(rv, rv);
const char* limit = data + size;
MetaElement * last = nsnull;
while (data < limit) {
const char* key = data;
PRUint32 keySize = strlen(key);
data += 1 + keySize;
if (data < limit) {
PRUint32 valueSize = strlen(data);
MetaElement *elem = new (data, valueSize) MetaElement;
if (!elem)
return NS_ERROR_OUT_OF_MEMORY;
elem->mKey.Assign(key);
// insert after last or as first element...
if (last) {
elem->mNext = last->mNext;
last->mNext = elem;
}
else {
elem->mNext = mData;
mData = elem;
}
last = elem;
data += 1 + valueSize;
// Adjust CacheMetaData size, 2 for the zero bytes of both strings
mMetaSize += 2 + keySize + valueSize;
}
memcpy(mBuffer, data, size);
mMetaSize = size;
}
return NS_OK;
}
@ -198,33 +143,34 @@ nsCacheMetaData::UnflattenMetaData(const char * data, PRUint32 size)
nsresult
nsCacheMetaData::VisitElements(nsICacheMetaDataVisitor * visitor)
{
MetaElement * elem = mData;
while (elem) {
PRBool keepGoing;
nsresult rv = visitor->VisitMetaDataElement(elem->mKey.get(), elem->mValue, &keepGoing);
const char * data = mBuffer;
const char * limit = mBuffer + mMetaSize;
while (data < limit) {
const char * key = data;
// Skip key part
data += strlen(data) + 1;
PRBool keepGoing;
nsresult rv = visitor->VisitMetaDataElement(key, data, &keepGoing);
if (NS_FAILED(rv) || !keepGoing)
break;
elem = elem->mNext;
// Skip value part
data += strlen(data) + 1;
}
return NS_OK;
}
void *
nsCacheMetaData::MetaElement::operator new(size_t size,
const char *value,
PRUint32 valueSize) CPP_THROW_NEW
nsresult
nsCacheMetaData::EnsureBuffer(PRUint32 bufSize)
{
size += valueSize;
MetaElement *elem = (MetaElement *) ::operator new(size);
if (!elem)
return nsnull;
memcpy(elem->mValue, value, valueSize);
elem->mValue[valueSize] = 0;
return elem;
}
if (mBufferSize < bufSize) {
char * buf = (char *)PR_REALLOC(mBuffer, bufSize);
if (!buf) {
return NS_ERROR_OUT_OF_MEMORY;
}
mBuffer = buf;
mBufferSize = bufSize;
}
return NS_OK;
}

View File

@ -42,48 +42,36 @@
#define _nsCacheMetaData_h_
#include "nspr.h"
#include "pldhash.h"
#include "nscore.h"
#include "nsString.h"
class nsICacheMetaDataVisitor;
class nsCacheMetaData {
public:
nsCacheMetaData();
~nsCacheMetaData() { Clear(); }
nsCacheMetaData() : mBuffer(nsnull), mBufferSize(0), mMetaSize(0) { }
void Clear();
PRBool IsEmpty() { return (mData == nsnull); }
~nsCacheMetaData() {
mBufferSize = mMetaSize = 0;
PR_FREEIF(mBuffer);
}
const char * GetElement(const char * key);
const char * GetElement(const char * key);
nsresult SetElement(const char * key,
const char * value);
nsresult SetElement(const char * key, const char * value);
PRUint32 Size(void) { return mMetaSize; }
PRUint32 Size(void) { return mMetaSize; }
nsresult FlattenMetaData(char * buffer, PRUint32 bufSize);
nsresult FlattenMetaData(char * buffer, PRUint32 bufSize);
nsresult UnflattenMetaData(const char * buffer, PRUint32 bufSize);
nsresult UnflattenMetaData(const char * buffer, PRUint32 bufSize);
nsresult VisitElements(nsICacheMetaDataVisitor * visitor);
nsresult VisitElements(nsICacheMetaDataVisitor * visitor);
private:
nsresult EnsureBuffer(PRUint32 size);
struct MetaElement
{
struct MetaElement * mNext;
nsCString mKey;
char mValue[1]; // actually, bigger than 1
// MetaElement and mValue are allocated together via:
void *operator new(size_t size,
const char *value,
PRUint32 valueSize) CPP_THROW_NEW;
};
MetaElement * mData;
char * mBuffer;
PRUint32 mBufferSize;
PRUint32 mMetaSize;
};