SYS_String.h

Go to the documentation of this file.

/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        SYS_String.h (SYS Library, C++)
 *
 * COMMENTS:
 *      System-independent string manipulation functions.
 */

#ifndef __SYS_String__
#define __SYS_String__

#include "SYS_API.h"

#include "SYS_Inline.h"
#include "SYS_Types.h"

#include <ctype.h>
#include <stdlib.h>
#include <string.h>

static inline constexpr uint32
SYSstring_hashseed(
        const char *str,
        exint length = SYS_EXINT_MAX,
        uint32 hash = 0,
        bool allow_nulls = false)
{
    if (!str || length <= 0 || (!allow_nulls && *str == '\0'))
        return hash;

    // A note on the magic number 37.
    // We want to scale by SOMETHING so that order is preserved.
    // That something should be prime and not a power of two to
    // avoid wrapping issues.
    // That something should be larger than our range of expected
    // values to avoid interference between consecutive letters.
    // 0-9a-z is 36 letters long.
    //
    // The real reason is that this is what Perl uses.
    if (!allow_nulls)
    {
        for (; length > 0 && *str != '\0'; length--, str++)
        {
            hash = (37 * hash) + (*str);
        }
    }
    else
    {
        for (; length > 0; length--, str++)
        {
            hash = (37 * hash) + (*str);
        }
    }

    // Make sure we never return zero for non-zero hash, since in many
    // cases we precompute string hashes and zero means "not initialized".
    // This allows us conforming values across different string
    // container implementations.
    if (hash == 0)
        hash = 1;

    return hash;
}

/// Generate a hash for a char string
static inline constexpr uint32
SYSstring_hash(
        const char *str,
        exint len = SYS_EXINT_MAX,
        bool allow_nulls = false)
{
    return SYSstring_hashseed(str, len, /*seed*/ 0, allow_nulls);
}

/// A standard name for a strtok that doesn't maintain state between calls.
/// This version is thus both reentrant and threadsafe.
/// SYSstrtok parses a string into a sequence of tokens. On the first call to
/// SYSstrtok, the string to be parsed must be specified as the parameter
/// 'string'. This parameter *will be modified* (destroying your copy).
/// 'delimit' specifies an array of single characters that will be used
/// as delimiters.
/// 'context' is a char * variable used internally by SYSstrtok to maintain
/// context between calls. Subsequent calls must specify the same unchanged
/// context variable as the first call.
/// To use SYSstrtok, on the first call first pass in your string as the 
/// parameter 'string'; on subsequent calls, pass it in as nullptr.
/// SYSstrtok returns non-empty strings pointing to the first non-delimiter
/// character of each token, or nullptr if no further tokens are available.
/// Example:
/// @code
/// char *string = strdup(getString());
/// char *strptr = string;
/// char *context;
/// char *token = SYSstrtok(string, MY_DELIMITERS, &context);
/// while (token)
/// {
///     do_some_stuff();
///     SYSstrtok(nullptr, MY_DELIMITERS, &context);
/// }
/// free(strptr);
/// @endcode
inline char *
SYSstrtok(char *string, const char *delimit, char **context)
{
#ifdef LINUX
    return strtok_r(string, delimit, context);
#else
    // MSVC 2003 doesn't have strtok_r. 2005 has strtok_s, which is the same
    // as strtok_r. Until we upgrade, use this C version of strtok_r.
    if (string == nullptr)
    {
        string = *context;
    }

    // Find and skip any leading delimiters.
    string += strspn(string, delimit);

    // There are only delimiters (or no text at all), so we've reached the end
    // of the string.
    if (*string == '\0')
    {
        *context = string;
        return nullptr;
    }

    // String now points at a token.
    char *token = string;

    // Find the end of the token.
    string = strpbrk(token, delimit);
    if (!string)
    {
        // This token is at the end of the string. Set the context to point at
        // the end of the string so on the next call, we'll return nullptr.
        *context = strchr(token, '\0');
    }
    else
    {
        // This is a token somewhere in the string. Set the found delimiter to
        // zero and initialize the context to the next character.
        *string = '\0';
        *context = string + 1;
    }

    return token;
#endif
}

/// The semantics for strncpy() leave a little to be desired
///  - If the buffer limit is hit, the string isn't guaranteed to be null
///     terminated.
///  - If the buffer limit isn't hit, the entire remainder of the string is
///     filled with nulls (which can be costly with large buffers).
/// The following implements the strlcpy() function from OpenBSD.  The function
/// is very similar to strncpy() but
///     The return code is the length of the src string
///     The resulting string is always null terminated (unless size == 0)
///     The remaining buffer is not touched
/// It's possible to check for errors by testing rcode >= size.
///
/// The size is the size of the buffer, not the portion of the sub-string to
/// copy.  If you want to only copy a portion of a string, make sure that the
/// @c size passed in is one @b larger than the length of the string since
/// SYSstrlcpy() will always ensure the string is null terminated.
///
/// It is invalid to pass a size of 0.
///
/// Examples: @code
///     char    buf[8];
///     strncpy(buf, "dog", 8)    // buf == ['d','o','g',0,0,0,0,0]
///     SYSstrlcpy(buf, "dog", 8) // buf == ['d','o','g',0,?,?,?,?]
///     strncpy(buf, "dog", 2)    // buf == ['d','o',0,0,0,0,0,0]
///     SYSstrlcpy(buf, "dog", 2) // buf == ['d',0,?,?,?,?,?,?]
///     SYSstrlcpy(buf, "dog", 3) // buf == ['d','o',0,?,?,?,?]
/// @endcode
inline size_t
SYSstrlcpy(char *dest, const char *src, size_t size)
{
    char *end = (char *)::memccpy(dest, src, 0, size);
    if (end)
    {
        return end - dest - 1;
    }
    // No null terminator found in the first size bytes
    if (size)
        dest[size-1] = 0;
    
    // Return rcode >= size to indicate that we would've busted the buffer.
    return size + 1;
}

/// The following implements the strlcpy() function from OpenBSD.  The
/// differences between strlcpy() and strncpy() are:
///     - The buffer will not be filled with null
///     - The size passed in is the full length of the buffer (not
///             remaining length)
///     - The dest will always be null terminated (unless it is already larger
///             than the size passed in)
/// The function returns strln(src) + SYSmin(size, strlen(dest))
/// If rcode >= size, truncation occurred
inline size_t
SYSstrlcat(char *dest, const char *src, size_t size)
{
    // Find the length of the dest buffer.  Only check for a null within the
    // allocated space of the buffer (i.e. we can't use strlen()).
    size_t dlen;
    for (dlen = 0; dlen < size; dlen++)
        if (!dest[dlen])
            break;
    if (dlen == size)
        return size + 1;        // Not enough space left
    // Now, copy the source over
    return dlen + SYSstrlcpy(dest+dlen, src, size-dlen);
}

inline int
SYSstrcasecmp(const char *a, const char *b)
{
    // Properly compare null strings, matching UT_String.
    if (!a || !b)
    {
        if (a) return 1;
        if (b) return -1;
        return 0;
    }
#if defined(WIN32)
    return ::stricmp(a, b);
#else
    return ::strcasecmp(a, b);
#endif
}

inline int
SYSstrcmp(const char *a, const char *b)
{
    // Properly compare null strings, matching UT_String.
    if (!a || !b)
    {
        if (a) return 1;
        if (b) return -1;
        return 0;
    }
    return ::strcmp(a, b);
}

#define WRAP_NULLTEST_C(FUNCTION, CONST) \
inline CONST char * \
SYS##FUNCTION(CONST char *s, int c) \
{ \
    if (!s) return nullptr; \
    return ::FUNCTION(s, c); \
} \
/**/

#define WRAP_NULLTEST(FUNCTION) \
WRAP_NULLTEST_C(FUNCTION, ) \
WRAP_NULLTEST_C(FUNCTION, const) \
/**/

// The standard does not specify behaviour on null strings, but it
// is reasonable to say a search token is never inside a null string,
// thereby increasing safety.
WRAP_NULLTEST(strchr)
WRAP_NULLTEST(strrchr)

#undef WRAP_NULLTEST
#undef WRAP_NULLTEST_C

inline int
SYSstrncasecmp(const char *a, const char *b, size_t n)
{
    if (!a || !b)
    {
        if (a) return 1;
        if (b) return -1;
        return 0;
    }
#if defined(WIN32)
    return ::strnicmp(a, b, n);
#else
    return ::strncasecmp(a, b, n);
#endif
}

/// Replacement for strcasestr, since no equivalent exists on Win32.
inline char *
SYSstrcasestr(const char *haystack, const char *needle)
{
#if defined(WIN32)
    // Designed for the normal case (small needle, large haystack).
    // Asymptotic cases will probably perform very poorly. For those, we'll
    // need: https://en.wikipedia.org/wiki/Boyer-Moore-Horspool_algorithm
     if (!haystack || !needle)
        return nullptr;

    // Empty needle gives beginning of string.
    if (!*needle)
        return const_cast<char *>(haystack);
    for(;;)
    {
        // Find the start of the pattern in the string.
        while(*haystack && tolower(*haystack) != tolower(*needle))
            haystack++;

        if (!*haystack)
            return nullptr;

        // Found the start of the pattern.
        const char *h = haystack, *n = needle;
        do
        {
            // End of needle? We found our man.
            if (!*++n)
                return const_cast<char *>(haystack);
            // End of haystack? Nothing more to look for.
            if (!*++h)
                return nullptr;
        } while(tolower(*h) == tolower(*n));

        haystack++;
    }
#else
    return const_cast<char*>(::strcasestr(const_cast<char*>(haystack),needle));
#endif
}

// Implementation of strndup for Windows.
inline char *
SYSstrndup(const char *s, size_t n)
{
#if defined(WIN32)
    size_t       l = ::strlen(s);
    if (l < n) n = l;
    char        *r = (char *)::malloc(n + 1);
    ::memcpy(r, s, n);
    r[n] = '\0';
    return r;
#else
    return ::strndup(s, n);
#endif
}

// On Windows, is*() methods are badly implemented.
// Running testut -i -t SYS_String shows about at least a 1.3x speed up.
#ifdef _WIN32
SYS_FORCE_INLINE bool
SYSisalpha(unsigned char c)
{
    // This test relies on promoting to unsigned integer
    return (unsigned(c & ~(1<<5)) - 'A') <= ('Z' - 'A');
}
SYS_FORCE_INLINE bool
SYSisdigit(unsigned char c)
{
    // Interestingly, this tends to perform better than one comparison
    return (c >= '0' && c <= '9');
}
#endif // _WIN32

// Windows decided in their infinite wisdom that negative values
// should crash their isfoo() functions, guard by only taking unsigned char
// arguments which get casted again to int's.

#define SYS_IS_WRAPPER(TEST)    \
SYS_FORCE_INLINE bool           \
SYS##TEST(unsigned char c)      \
{                               \
    return TEST(c);             \
}                               \
/**/

SYS_IS_WRAPPER(isalnum)
#ifndef _WIN32
SYS_IS_WRAPPER(isalpha)
#endif
// isascii is specifically marked deprecated
// SYS_IS_WRAPPER(isascii)
// This does have a POSIX standard, but isn't in Windows.
// SYS_IS_WRAPPER(isblank)
SYS_IS_WRAPPER(iscntrl)
#ifndef _WIN32
SYS_IS_WRAPPER(isdigit)
#endif
SYS_IS_WRAPPER(isgraph)
SYS_IS_WRAPPER(islower)
SYS_IS_WRAPPER(isprint)
SYS_IS_WRAPPER(ispunct)
// isspace is rather important we get very, very, fast.
// SYS_IS_WRAPPER(isspace)
SYS_IS_WRAPPER(isupper)
SYS_IS_WRAPPER(isxdigit)

#undef SYS_IS_WRAPPER

    static SYS_FORCE_INLINE const void *
    SYSmemrchr(const void *v, int c, exint n)
    {
#if defined(LINUX)
        return ::memrchr(v, c, n);
#else
        const unsigned char *beg = (const unsigned char *)v;
        const unsigned char *full_end = (const unsigned char *)v + n;
        const unsigned char *end = (const unsigned char *)v + (n/4)*4;
        for (const unsigned char *s = full_end; s-->end;)
        {
            if (*s == c)
                return s;
        }
        for (const unsigned char *s = end-1; s > beg;)
        {
            if (*s == c) return s;
            --s;
            if (*s == c) return s;
            --s;
            if (*s == c) return s;
            --s;
            if (*s == c) return s;
            --s;
        }
        return nullptr;
#endif
    }

static SYS_FORCE_INLINE constexpr int
SYSmemcmp(const void *lhs, const void *rhs, size_t count)
{
    return __builtin_memcmp(lhs, rhs, count);
}

#define CREATE_SYSisspace(TYPE)         \
inline bool                             \
SYSisspace(TYPE c)                      \
{                                       \
    /* Fastest exit for non-spaces. */  \
    if (c > ' ')                        \
        return false;                   \
    /* Either equal to space, or between tab and carriage return */ \
    return (c == ' ' || (c <= '\xd' && c >= '\x9'));    \
}

CREATE_SYSisspace(int)
CREATE_SYSisspace(unsigned char)
CREATE_SYSisspace(signed char)

#undef CREATE_SYSisspace


#endif