stringutils.h

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/* Copyright (C) 2004-2023 Olly Betts
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see
 * <https://www.gnu.org/licenses/>.
 */
 
#ifndef XAPIAN_INCLUDED_STRINGUTILS_H
#define XAPIAN_INCLUDED_STRINGUTILS_H
 
// Hack to allow inclusion from xapian-omega.
// FIXME: Move C_isalpha(), etc to the public API?
#define XAPIAN_IN_XAPIAN_H
#include <xapian/constinfo.h>
#undef XAPIAN_IN_XAPIAN_H
 
#include <algorithm>
#include <string>
#include <string_view>
#include <cstring>
 
#define STRINGIZE_(X) #X
 
#define STRINGIZE(X) STRINGIZE_(X)
 
#define CONST_STRLEN(S) (sizeof(S"") - 1)
 
/* C++20 added starts_with(), ends_with() and contains() methods to std::string
 * and std::string_view which provide this functionality, but we don't yet
 * require C++20.
 */
 
inline bool
startswith(std::string_view s, char pfx)
{
    return !s.empty() && s[0] == pfx;
}
 
inline bool
startswith(std::string_view s, const char* pfx, size_t len)
{
    return s.size() >= len && (std::memcmp(s.data(), pfx, len) == 0);
}
 
inline bool
startswith(std::string_view s, const char* pfx)
{
    return startswith(s, pfx, std::strlen(pfx));
}
 
inline bool
startswith(std::string_view s, std::string_view pfx)
{
    return startswith(s, pfx.data(), pfx.size());
}
 
inline bool
endswith(std::string_view s, char sfx)
{
    return !s.empty() && s[s.size() - 1] == sfx;
}
 
inline bool
endswith(std::string_view s, const char* sfx, size_t len)
{
    return s.size() >= len && (std::memcmp(s.data() + s.size() - len, sfx, len) == 0);
}
 
inline bool
endswith(std::string_view s, const char* sfx)
{
    return endswith(s, sfx, std::strlen(sfx));
}
 
inline bool
endswith(std::string_view s, std::string_view sfx)
{
    return endswith(s, sfx.data(), sfx.size());
}
 
inline bool
contains(std::string_view s, char substring)
{
    return s.find(substring) != s.npos;
}
 
inline bool
contains(std::string_view s, const char* substring, size_t len)
{
    return s.find(substring, 0, len) != s.npos;
}
 
inline bool
contains(std::string_view s, const char* substring)
{
    return s.find(substring) != s.npos;
}
 
inline bool
contains(std::string_view s, std::string_view substring)
{
    return s.find(substring) != s.npos;
}
 
inline std::string::size_type
common_prefix_length(std::string_view a, std::string_view b)
{
    std::string::size_type minlen = std::min(a.size(), b.size());
    std::string::size_type common;
    for (common = 0; common < minlen; ++common) {
        if (a[common] != b[common]) break;
    }
    return common;
}
 
inline std::string::size_type
common_prefix_length(std::string_view a, std::string_view b,
                     std::string::size_type max_prefix_len)
{
    std::string::size_type minlen = std::min({a.size(),
                                              b.size(),
                                              max_prefix_len});
    std::string::size_type common;
    for (common = 0; common < minlen; ++common) {
        if (a[common] != b[common]) break;
    }
    return common;
}
 
// Like C's isXXXXX() but:
//  (a) always work in the C locale
//  (b) handle signed char as well as unsigned char
//  (c) have a suitable signature for use as predicates with find_if()
//  (d) add negated versions isnotXXXXX() which are useful as predicates
 
namespace Xapian {
    namespace Internal {
        const unsigned char HEX_MASK = 0x0f;
        const unsigned char IS_UPPER = 0x10;
        const unsigned char IS_ALPHA = 0x20; // NB Same as ASCII "case bit".
        const unsigned char IS_DIGIT = 0x40;
        const unsigned char IS_SPACE = 0x80;
    }
}
 
// FIXME: These functions assume ASCII or an ASCII compatible character set
// such as ISO-8859-N or UTF-8.  EBCDIC would need some work (patches
// welcome!)
static_assert('\x20' == ' ', "character set isn't a superset of ASCII");
 
// Add explicit conversion to bool to prevent compiler warning from "aCC +w":
// Warning (suggestion) 818: [...] # Type `int' is larger than type `bool',
// truncation in value may result.
 
inline unsigned char C_tab_(char ch) {
    const unsigned char * C_tab = Xapian::Internal::get_constinfo_()->C_tab;
    return C_tab[static_cast<unsigned char>(ch)];
}
 
inline bool C_isdigit(char ch) {
    using namespace Xapian::Internal;
    return bool(C_tab_(ch) & IS_DIGIT);
}
 
inline bool C_isxdigit(char ch) {
    using namespace Xapian::Internal;
    // Include IS_DIGIT so '0' gives true.
    return bool(C_tab_(ch) & (HEX_MASK|IS_DIGIT));
}
 
inline bool C_isupper(char ch) {
    using namespace Xapian::Internal;
    return bool(C_tab_(ch) & IS_UPPER);
}
 
inline bool C_islower(char ch) {
    using namespace Xapian::Internal;
    return (C_tab_(ch) & (IS_ALPHA|IS_UPPER)) == IS_ALPHA;
}
 
inline bool C_isalpha(char ch) {
    using namespace Xapian::Internal;
    return bool(C_tab_(ch) & IS_ALPHA);
}
 
inline bool C_isalnum(char ch) {
    using namespace Xapian::Internal;
    return bool(C_tab_(ch) & (IS_ALPHA|IS_DIGIT));
}
 
inline bool C_isspace(char ch) {
    using namespace Xapian::Internal;
    return bool(C_tab_(ch) & IS_SPACE);
}
 
inline bool C_isnotdigit(char ch) { return !C_isdigit(ch); }
inline bool C_isnotxdigit(char ch) { return !C_isxdigit(ch); }
inline bool C_isnotupper(char ch) { return !C_isupper(ch); }
inline bool C_isnotlower(char ch) { return !C_islower(ch); }
inline bool C_isnotalpha(char ch) { return !C_isalpha(ch); }
inline bool C_isnotalnum(char ch) { return !C_isalnum(ch); }
inline bool C_isnotspace(char ch) { return !C_isspace(ch); }
 
inline char C_tolower(char ch) {
    using namespace Xapian::Internal;
    return ch | (C_tab_(ch) & IS_ALPHA);
}
 
inline char C_toupper(char ch) {
    using namespace Xapian::Internal;
    return ch &~ (C_tab_(ch) & IS_ALPHA);
}
 
inline int hex_digit(char ch) {
    using namespace Xapian::Internal;
    return C_tab_(ch) & HEX_MASK;
}
 
inline char hex_decode(char ch1, char ch2) {
    return char(hex_digit(ch1) << 4 | hex_digit(ch2));
}
 
#endif // XAPIAN_INCLUDED_STRINGUTILS_H