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[rtext] Use libc for TextLength(), TextCopy(), TextSubtext() and TextInsert() #4911

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[rtext] Use libc for TextLength(), TextCopy(), TextSubtext() and TextInsert() #4911

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37 changes: 11 additions & 26 deletions src/rtext.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1401,9 +1401,7 @@ unsigned int TextLength(const char *text)

if (text != NULL)
{
// NOTE: Alternative: use strlen(text)

while (*text++) length++;
length = strlen(text);
}

return length;
Expand Down Expand Up @@ -1497,20 +1495,13 @@ int TextCopy(char *dst, const char *src)
{
int bytes = 0;

if ((src != NULL) && (dst != NULL))
// strcpy is marked restrict, meaning src and dst must not alias.
// Attempt to defend against that, but this is not fully robust
// as someone could pass in two sub-portions of the same string.
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@williewillus williewillus Apr 27, 2025 •
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note that this is also already a problem with the preexisting code, so we aren't necessarily regressing here

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The function prototype of TextCopy should probably be marked restrict since strcpy already is. Alternative is to use memmove instead of strcpy to protect against aliasing.

Copy does implicitly signal that two non-overlapping memory regions should be used, however there is risk that some developer has used this function to copy into overlapping memory regions. Strcpy will break such code, whilst memmove will not.

Alternate suggested code:

bytes = strlen(src);
memmove(dst, src, bytes);

if ((src != NULL) && (dst != NULL) && (src != dst))
{
// NOTE: Alternative: use strcpy(dst, src)

while (*src != '\0')
{
*dst = *src;
dst++;
src++;

bytes++;
}

*dst = '\0';
strcpy(dst, src);
bytes = strlen(src);
}

return bytes;
Expand Down Expand Up @@ -1547,13 +1538,7 @@ const char *TextSubtext(const char *text, int position, int length)
if (length > maxLength) length = maxLength;
if (length >= MAX_TEXT_BUFFER_LENGTH) length = MAX_TEXT_BUFFER_LENGTH - 1;

// NOTE: Alternative: memcpy(buffer, text + position, length)

for (int c = 0 ; c < length ; c++)
{
buffer[c] = text[position + c];
}

memcpy(buffer, text + position, length);
buffer[length] = '\0';

return buffer;
Expand Down Expand Up @@ -1618,9 +1603,9 @@ char *TextInsert(const char *text, const char *insert, int position)

char *result = (char *)RL_MALLOC(textLen + insertLen + 1);

for (int i = 0; i < position; i++) result[i] = text[i];
for (int i = position; i < insertLen + position; i++) result[i] = insert[i];
for (int i = (insertLen + position); i < (textLen + insertLen); i++) result[i] = text[i];
memcpy(result, text, position);
memcpy(result + position, insert, insertLen);
memcpy(result + position + insertLen, text + position, textLen - position);

result[textLen + insertLen] = '\0'; // Make sure text string is valid!

Expand Down