Hi Enrico & Daniel,
Thanks all, I'm browsing through the formatters page. I managed to throw
together a skeleton, but it doesn't seem to work too well. Maybe I failed to
grasp something:
import lldb
def UniString_SummaryProvider(valobj, dict):
e = lldb.SBError()
s = u'"'
if valobj.GetValue() != 0:
content = valobj.GetChildMemberWithName('content')
length = content.GetPointeeData(0,1).GetChildMemberWithName('length')
string = content.GetPointeeData(0,1).GetChildMemberWithName('string')
i = 0
newchar = -1
while newchar != 0 and i < length:
# read next wchar character out of memory
data_val = string.GetPointeeData(i, 1)
newchar = data_val.GetUnsignedInt16(e, 0) # utf-16
if e.fail:
return '<error>'
i = i + 1
# add the character to our string 's'
if newchar != 0:
s = s + unichr(newchar)
s = s + u'"'
return s.encode('utf-8')
def __lldb_init_module(debugger,dict):
debugger.HandleCommand("type summary add -F
UniString.UniString_SummaryProvider GS::UniString")
Yes, I'd like to show the string member (it's in UTF-16) in the summary. I was
looking at the CFString.py formatter, but that seems to be an overkill in our
case.
The string[1] member is an 'old' C trick, here's the allocation routine. It
preallocates a separate buffer of the right size, then uses placement new to
put the SharedBuffer member there.
inline GS::UniString::SharedBuffer::SharedBuffer (USize initialLength, USize
initialCapacity, Int32 initialRefCounter):
length (initialLength),
capacity (initialCapacity),
refCounter (initialRefCounter)
{
}
inline USize GS::UniString::CapacityToBufferSize (USize capacity)
{
return (sizeof (SharedBuffer) + (capacity - 1) * sizeof (unichar));
}
inline USize GS::UniString::BufferSizeToCapacity (USize bufferSize)
{
return ((bufferSize - sizeof (SharedBuffer)) / sizeof (unichar) + 1);
}
GS::UniString::SharedBuffer* GS::UniString::AllocateBuffer (USize capacity)
{
if (capacity == 0)
return ShareEmptyBuffer ();
capacity++; // to ensure capacity for the closing 0 (used in conversion)
USize bufferSize = CapacityToBufferSize (capacity);
if (bufferSize < MinBufferSize4) {
if (bufferSize < MinBufferSize1)
bufferSize = MinBufferSize1;
else if (bufferSize < MinBufferSize2)
bufferSize = MinBufferSize2;
else if (bufferSize < MinBufferSize3)
bufferSize = MinBufferSize3;
else
bufferSize = MinBufferSize4;
}
void* buffer = cachedAllocator.Allocate (bufferSize, &bufferSize);
capacity = BufferSizeToCapacity (bufferSize);
return new (buffer) SharedBuffer (0, capacity, 1);
}
Best, Akos
On Dec 10, 2012, at 11:32 PM, Enrico Granata
<[email protected]<mailto:[email protected]>>
wrote:
Hi.
It looks like your task should be relatively easy since you have the full
definition of the UniString and the SharedBuffer.
I am assuming you will want to show the string content as your summary (as it
happens for std::string and NSString).
If so, how are you going to use the string buffer? Is it going to contain a
pointer to the real data?
I am probably slightly confused by your comment next to it.
Could you explain the logic for storing the string data or provide an example
of code that handles e.g. the string allocation, or access to it?
Given that understanding, it should be relatively straightforward to accomplish
your task.
Enrico Granata
✉ egranata@.com
✆ (408) 972-7683
On Dec 10, 2012, at 7:35 AM, "Somorjai, Akos"
<[email protected]<mailto:[email protected]>> wrote:
Hello everyone,
I need a little help with a custom formatter for the class below; I'd
appreciate if someone could throw together a skeleton I can start from.
Thanks,
Akos
Here's the class layout:
class UniString {
private:
struct SharedBuffer;
SharedBuffer* content; // shared buffer storing content of the string
// Implementation classes and structures
struct SharedBuffer {
USize length; // length of the string in UniChar::Layout units
USize capacity; // capacity of the allocated buffer in UniChar::Layout units
SInt32 refCounter; // stores number of references to this shared buffer
char reserved[2]; // padding reserved for the future use
unichar string[1]; // buffer storing content of the string (extends beyond of
the SharedBuffer)
inline SharedBuffer ();
inline SharedBuffer (USize initialLength, USize initialCapacity, Int32
initialRefCounter);
};
…
};
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