add libc primitives to reduce dependencies

src/libc.c

@@ -0,0 +1,247 @@
+/* ----------------------------------------------------------------------------
+Copyright (c) 2018-2023, Microsoft Research, Daan Leijen
+This is free software; you can redistribute it and/or modify it under the
+terms of the MIT license. A copy of the license can be found in the file
+"LICENSE" at the root of this distribution.
+-----------------------------------------------------------------------------*/
+
+// --------------------------------------------------------
+// This module defines various std libc functions to reduce
+// the dependency on libc, and also prevent errors caused 
+// by some libc implementations when called before `main`
+// executes (due to malloc redirection)
+// --------------------------------------------------------
+
+#include "mimalloc.h"
+#include "mimalloc/internal.h"
+#include "mimalloc/prim.h"      // mi_prim_getenv
+
+char _mi_toupper(char c) {
+  if (c >= 'a' && c <= 'z') return (c - 'a' + 'A');
+                       else return c;
+}
+
+int _mi_strnicmp(const char* s, const char* t, size_t n) {
+  if (n == 0) return 0;
+  for (; *s != 0 && *t != 0 && n > 0; s++, t++, n--) {
+    if (_mi_toupper(*s) != _mi_toupper(*t)) break;
+  }
+  return (n == 0 ? 0 : *s - *t);
+}
+
+void _mi_strlcpy(char* dest, const char* src, size_t dest_size) {
+  if (dest==NULL || src==NULL || dest_size == 0) return;
+  // copy until end of src, or when dest is (almost) full
+  while (*src != 0 && dest_size > 1) {
+    *dest++ = *src++;
+    dest_size--;
+  }
+  // always zero terminate
+  *dest = 0;
+}
+
+void _mi_strlcat(char* dest, const char* src, size_t dest_size) {
+  if (dest==NULL || src==NULL || dest_size == 0) return;
+  // find end of string in the dest buffer
+  while (*dest != 0 && dest_size > 1) {
+    dest++;
+    dest_size--;
+  }
+  // and catenate
+  _mi_strlcpy(dest, src, dest_size);
+}
+
+size_t _mi_strlen(const char* s) {
+  if (s==NULL) return 0;
+  size_t len = 0;
+  while(s[len] != 0) { len++; }
+  return len;
+}
+
+size_t _mi_strnlen(const char* s, size_t max_len) {
+  if (s==NULL) return 0;
+  size_t len = 0;
+  while(s[len] != 0 && len < max_len) { len++; }
+  return len;
+}
+
+#ifdef MI_NO_GETENV
+bool _mi_getenv(const char* name, char* result, size_t result_size) {
+  MI_UNUSED(name);
+  MI_UNUSED(result);
+  MI_UNUSED(result_size);
+  return false;
+}
+#else
+bool _mi_getenv(const char* name, char* result, size_t result_size) {
+  if (name==NULL || result == NULL || result_size < 64) return false;
+  return _mi_prim_getenv(name,result,result_size);
+}
+#endif
+
+// --------------------------------------------------------
+// Define our own limited `_vsnprintf` 
+// --------------------------------------------------------
+
+static void mi_outc(char c, char** out, char* end) {
+  char* p = *out;
+  if (p >= end) return;
+  *p = c;
+  *out = p + 1;
+}
+
+static void mi_outs(const char* s, char** out, char* end) {
+  if (s == NULL) return;
+  char* p = *out;
+  while (*s != 0 && p < end) {
+    *p++ = *s++;
+  }
+  *out = p;
+}
+
+static void mi_out_fill(char fill, size_t len, char** out, char* end) {
+  char* p = *out;
+  for (size_t i = 0; i < len && p < end; i++) {
+    *p++ = fill;
+  }
+  *out = p;
+}
+
+static void mi_out_alignright(char fill, char* start, size_t len, size_t extra, char* end) {
+  if (len == 0 || extra == 0) return;
+  if (start + len + extra >= end) return;
+  // move `len` characters to the right (in reverse since it can overlap)
+  for (size_t i = 1; i <= len; i++) {
+    start[len + extra - i] = start[len - i];
+  }
+  // and fill the start
+  for (size_t i = 0; i < extra; i++) {
+    start[i] = fill;
+  }
+}
+
+
+static void mi_out_num(uintptr_t x, size_t base, char prefix, char** out, char* end) 
+{
+  if (x == 0 || base == 0 || base > 16) {
+    if (prefix != 0) { mi_outc(prefix, out, end); }
+    mi_outc('0',out,end);
+  }
+  else {
+    // output digits in reverse
+    char* start = *out;
+    while (x > 0) {
+      char digit = (char)(x % base);
+      mi_outc((digit <= 9 ? '0' + digit : 'A' + digit - 10),out,end);
+      x = x / base;
+    }
+    if (prefix != 0) { 
+      mi_outc(prefix, out, end); 
+    }
+    size_t len = *out - start;
+    // and reverse in-place
+    for (size_t i = 0; i < (len / 2); i++) {
+      char c = start[len - i - 1];
+      start[len - i - 1] = start[i];
+      start[i] = c;
+    }
+  }
+}
+
+
+#define MI_NEXTC()  c = *in; if (c==0) break; in++;
+
+void _mi_vsnprintf(char* buf, size_t bufsize, const char* fmt, va_list args) {
+  if (buf == NULL || bufsize == 0 || fmt == NULL) return;
+  buf[bufsize - 1] = 0;
+  char* const end = buf + (bufsize - 1);
+  const char* in = fmt;
+  char* out = buf;
+  while (true) {
+    if (out >= end) break;
+    char c;
+    MI_NEXTC();
+    if (c != '%') {
+      mi_outc(c,&out,end);
+    }
+    else {
+      MI_NEXTC();
+      char   fill = ' ';
+      size_t width = 0;
+      char   numtype = 'd';
+      char   numplus = 0;
+      bool   alignright = true; 
+      if (c == '+' || c == ' ') { numplus = c; MI_NEXTC(); }
+      if (c == '-') { alignright = false; MI_NEXTC(); }
+      if (c == '0') { fill = '0'; MI_NEXTC(); }
+      if (c >= '1' && c <= '9') {
+        width = (c - '0'); MI_NEXTC();
+        while (c >= '0' && c <= '9') {
+          width = (10 * width) + (c - '0'); MI_NEXTC();
+        }
+        if (c == 0) break;  // extra check due to while
+      }      
+      if (c == 'z' || c == 'l') { numtype = c; MI_NEXTC(); }
+
+      char* const start = out;
+      if (c == 's') {
+        // string
+        const char* s = va_arg(args, const char*);
+        mi_outs(s, &out, end);
+      }
+      else if (c == 'p' || c == 'x' || c == 'u') {
+        // unsigned
+        uintptr_t x = 0;
+        if (c == 'x' || c == 'u') {
+          if (numtype == 'z') x = va_arg(args, size_t);
+                         else x = va_arg(args, unsigned long);
+        }
+        else if (c == 'p') {
+          x = va_arg(args, uintptr_t);
+          mi_outs("0x", &out, end);
+          if (width == 0) {
+            width = 2 * sizeof(void*);
+            fill = '0';
+          }
+        }
+        mi_out_num(x, (c == 'x' || c == 'p' ? 16 : 10), numplus, &out, end);
+      }
+      else if (c == 'i' || c == 'd') {
+        // signed
+        long x = va_arg(args, long);
+        char pre = 0;
+        if (x < 0) {
+          pre = '-';
+          x = -x;
+        }
+        else if (numplus != 0) {
+          pre = numplus;
+        }
+        mi_out_num((size_t)x, 10, pre, &out, end);
+      }
+      else if (c >= ' ' && c < '~') {
+        mi_outc(c, &out, end);
+      }
+
+      // fill & align
+      mi_assert_internal(out <= end);
+      mi_assert_internal(out >= start);
+      const size_t len = out - start;
+      if (len < width) {
+        mi_out_fill(fill, width - len, &out, end);
+        if (alignright && out <= end) {
+          mi_out_alignright(fill, start, len, width - len, end);
+        }
+      }
+    }
+  }
+  mi_assert_internal(out <= end);
+  *out = 0;
+}
+
+void _mi_snprintf(char* buf, size_t buflen, const char* fmt, ...) {
+  va_list args;
+  va_start(args, fmt);
+  _mi_vsnprintf(buf, buflen, fmt, args);
+  va_end(args);
+}