picom/src/string_utils.c

// SPDX-License-Identifier: MPL-2.0
// Copyright (c) Yuxuan Shui <yshuiv7@gmail.com>

#include <string.h>

#include "compiler.h"
#include "string_utils.h"
#include "utils.h"

#pragma GCC diagnostic push

// gcc warns about legitimate strncpy in mstrjoin and mstrextend
// strncpy(str, src1, len1) intentional truncates the null byte from src1.
// strncpy(str+len1, src2, len2) uses bound depends on the source argument,
// but str is allocated with len1+len2+1, so this strncpy can't overflow
#pragma GCC diagnostic ignored "-Wpragmas"
#pragma GCC diagnostic ignored "-Wstringop-truncation"
#pragma GCC diagnostic ignored "-Wstringop-overflow"

/**
 * Allocate the space and join two strings.
 */
char *mstrjoin(const char *src1, const char *src2) {
	auto len1 = strlen(src1);
	auto len2 = strlen(src2);
	auto len = len1 + len2 + 1;
	auto str = ccalloc(len, char);

	strncpy(str, src1, len1);
	strncpy(str + len1, src2, len2);
	str[len - 1] = '\0';

	return str;
}

/**
 * Concatenate a string on heap with another string.
 */
void mstrextend(char **psrc1, const char *src2) {
	if (!*psrc1) {
		*psrc1 = strdup(src2);
		return;
	}

	auto len1 = strlen(*psrc1);
	auto len2 = strlen(src2);
	auto len = len1 + len2 + 1;
	*psrc1 = crealloc(*psrc1, len);

	strncpy(*psrc1 + len1, src2, len2);
	(*psrc1)[len - 1] = '\0';
}

#pragma GCC diagnostic pop

/// Parse a floating point number of form (+|-)?[0-9]*(\.[0-9]*)
double strtod_simple(const char *src, const char **end) {
  double neg = 1;
  if (*src == '-') {
    neg = -1;
    src++;
  } else if (*src == '+') {
    src++;
  }

  double ret = 0;
  while (*src >= '0' && *src <= '9') {
    ret = ret * 10 + (*src - '0');
    src++;
  }

  if (*src == '.') {
    double frac = 0, mult = 0.1;
    src++;
    while (*src >= '0' && *src <= '9') {
      frac += mult * (*src - '0');
      mult *= 0.1;
      src++;
    }
    ret += frac;
  }

  *end = src;
  return ret * neg;
}