Initial Vexta Core v0.1.0 release

src/compat/assumptions.h

@@ -0,0 +1,57 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2020 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+// Compile-time verification of assumptions we make.
+
+#ifndef DIGIBYTE_COMPAT_ASSUMPTIONS_H
+#define DIGIBYTE_COMPAT_ASSUMPTIONS_H
+
+#include <limits>
+
+// Assumption: We assume that the macro NDEBUG is not defined.
+// Example(s): We use assert(...) extensively with the assumption of it never
+//             being a noop at runtime.
+#if defined(NDEBUG)
+# error "Vexta cannot be compiled without assertions."
+#endif
+
+// Assumption: We assume a C++17 (ISO/IEC 14882:2017) compiler (minimum requirement).
+// Example(s): We assume the presence of C++17 features everywhere :-)
+// ISO Standard C++17 [cpp.predefined]p1:
+// "The name __cplusplus is defined to the value 201703L when compiling a C++
+//  translation unit."
+static_assert(__cplusplus >= 201703L, "C++17 standard assumed");
+
+// Assumption: We assume the floating-point types to fulfill the requirements of
+//             IEC 559 (IEEE 754) standard.
+// Example(s): Floating-point division by zero in ConnectBlock, CreateTransaction
+//             and EstimateMedianVal.
+static_assert(std::numeric_limits<float>::is_iec559, "IEEE 754 float assumed");
+static_assert(std::numeric_limits<double>::is_iec559, "IEEE 754 double assumed");
+
+// Assumption: We assume eight bits per byte (obviously, but remember: don't
+//             trust -- verify!).
+// Example(s): Everywhere :-)
+static_assert(std::numeric_limits<unsigned char>::digits == 8, "8-bit byte assumed");
+
+// Assumption: We assume integer widths.
+// Example(s): GetSizeOfCompactSize and WriteCompactSize in the serialization
+//             code.
+static_assert(sizeof(short) == 2, "16-bit short assumed");
+static_assert(sizeof(int) == 4, "32-bit int assumed");
+static_assert(sizeof(unsigned) == 4, "32-bit unsigned assumed");
+
+// Assumption: We assume size_t to be 32-bit or 64-bit.
+// Example(s): size_t assumed to be at least 32-bit in ecdsa_signature_parse_der_lax(...).
+//             size_t assumed to be 32-bit or 64-bit in MallocUsage(...).
+static_assert(sizeof(size_t) == 4 || sizeof(size_t) == 8, "size_t assumed to be 32-bit or 64-bit");
+static_assert(sizeof(size_t) == sizeof(void*), "Sizes of size_t and void* assumed to be equal");
+
+// Some important things we are NOT assuming (non-exhaustive list):
+// * We are NOT assuming a specific value for std::endian::native.
+// * We are NOT assuming a specific value for std::locale("").name().
+// * We are NOT assuming a specific value for std::numeric_limits<char>::is_signed.
+
+#endif // DIGIBYTE_COMPAT_ASSUMPTIONS_H

src/compat/byteswap.h

@@ -0,0 +1,60 @@
+// Copyright (c) 2014-2019 The Bitcoin Core developers
+// Copyright (c) 2014-2019 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef DIGIBYTE_COMPAT_BYTESWAP_H
+#define DIGIBYTE_COMPAT_BYTESWAP_H
+
+#if defined(HAVE_CONFIG_H)
+#include <config/vexta-config.h>
+#endif
+
+#include <stdint.h>
+
+#if defined(HAVE_BYTESWAP_H)
+#include <byteswap.h>
+#endif
+
+#if defined(MAC_OSX)
+
+#include <libkern/OSByteOrder.h>
+#define bswap_16(x) OSSwapInt16(x)
+#define bswap_32(x) OSSwapInt32(x)
+#define bswap_64(x) OSSwapInt64(x)
+
+#else
+// Non-MacOS / non-Darwin
+
+#if HAVE_DECL_BSWAP_16 == 0
+inline uint16_t bswap_16(uint16_t x)
+{
+    return (x >> 8) | (x << 8);
+}
+#endif // HAVE_DECL_BSWAP16 == 0
+
+#if HAVE_DECL_BSWAP_32 == 0
+inline uint32_t bswap_32(uint32_t x)
+{
+    return (((x & 0xff000000U) >> 24) | ((x & 0x00ff0000U) >>  8) |
+            ((x & 0x0000ff00U) <<  8) | ((x & 0x000000ffU) << 24));
+}
+#endif // HAVE_DECL_BSWAP32 == 0
+
+#if HAVE_DECL_BSWAP_64 == 0
+inline uint64_t bswap_64(uint64_t x)
+{
+     return (((x & 0xff00000000000000ull) >> 56)
+          | ((x & 0x00ff000000000000ull) >> 40)
+          | ((x & 0x0000ff0000000000ull) >> 24)
+          | ((x & 0x000000ff00000000ull) >> 8)
+          | ((x & 0x00000000ff000000ull) << 8)
+          | ((x & 0x0000000000ff0000ull) << 24)
+          | ((x & 0x000000000000ff00ull) << 40)
+          | ((x & 0x00000000000000ffull) << 56));
+}
+#endif // HAVE_DECL_BSWAP64 == 0
+
+#endif // defined(MAC_OSX)
+
+#endif // DIGIBYTE_COMPAT_BYTESWAP_H

src/compat/cpuid.h

@@ -0,0 +1,24 @@
+// Copyright (c) 2017-2019 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef DIGIBYTE_COMPAT_CPUID_H
+#define DIGIBYTE_COMPAT_CPUID_H
+
+#if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
+#define HAVE_GETCPUID
+
+#include <cpuid.h>
+
+// We can't use cpuid.h's __get_cpuid as it does not support subleafs.
+void static inline GetCPUID(uint32_t leaf, uint32_t subleaf, uint32_t& a, uint32_t& b, uint32_t& c, uint32_t& d)
+{
+#ifdef __GNUC__
+    __cpuid_count(leaf, subleaf, a, b, c, d);
+#else
+  __asm__ ("cpuid" : "=a"(a), "=b"(b), "=c"(c), "=d"(d) : "0"(leaf), "2"(subleaf));
+#endif
+}
+
+#endif // defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
+#endif // DIGIBYTE_COMPAT_CPUID_H

src/compat/endian.h

@@ -0,0 +1,242 @@
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2014-2020 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef DIGIBYTE_COMPAT_ENDIAN_H
+#define DIGIBYTE_COMPAT_ENDIAN_H
+
+#if defined(HAVE_CONFIG_H)
+#include <config/vexta-config.h>
+#endif
+
+#include <compat/byteswap.h>
+
+#include <stdint.h>
+
+#if defined(HAVE_ENDIAN_H)
+#include <endian.h>
+#elif defined(HAVE_SYS_ENDIAN_H)
+#include <sys/endian.h>
+#endif
+
+#ifndef HAVE_CONFIG_H
+// While not technically a supported configuration, defaulting to defining these
+// DECLs when we were compiled without autotools makes it easier for other build
+// systems to build things like libvextaconsensus for strange targets.
+#ifdef htobe16
+#define HAVE_DECL_HTOBE16 1
+#endif
+#ifdef htole16
+#define HAVE_DECL_HTOLE16 1
+#endif
+#ifdef be16toh
+#define HAVE_DECL_BE16TOH 1
+#endif
+#ifdef le16toh
+#define HAVE_DECL_LE16TOH 1
+#endif
+
+#ifdef htobe32
+#define HAVE_DECL_HTOBE32 1
+#endif
+#ifdef htole32
+#define HAVE_DECL_HTOLE32 1
+#endif
+#ifdef be32toh
+#define HAVE_DECL_BE32TOH 1
+#endif
+#ifdef le32toh
+#define HAVE_DECL_LE32TOH 1
+#endif
+
+#ifdef htobe64
+#define HAVE_DECL_HTOBE64 1
+#endif
+#ifdef htole64
+#define HAVE_DECL_HTOLE64 1
+#endif
+#ifdef be64toh
+#define HAVE_DECL_BE64TOH 1
+#endif
+#ifdef le64toh
+#define HAVE_DECL_LE64TOH 1
+#endif
+
+#endif // HAVE_CONFIG_H
+
+#if defined(WORDS_BIGENDIAN)
+
+#if HAVE_DECL_HTOBE16 == 0
+inline uint16_t htobe16(uint16_t host_16bits)
+{
+    return host_16bits;
+}
+#endif // HAVE_DECL_HTOBE16
+
+#if HAVE_DECL_HTOLE16 == 0
+inline uint16_t htole16(uint16_t host_16bits)
+{
+    return bswap_16(host_16bits);
+}
+#endif // HAVE_DECL_HTOLE16
+
+#if HAVE_DECL_BE16TOH == 0
+inline uint16_t be16toh(uint16_t big_endian_16bits)
+{
+    return big_endian_16bits;
+}
+#endif // HAVE_DECL_BE16TOH
+
+#if HAVE_DECL_LE16TOH == 0
+inline uint16_t le16toh(uint16_t little_endian_16bits)
+{
+    return bswap_16(little_endian_16bits);
+}
+#endif // HAVE_DECL_LE16TOH
+
+#if HAVE_DECL_HTOBE32 == 0
+inline uint32_t htobe32(uint32_t host_32bits)
+{
+    return host_32bits;
+}
+#endif // HAVE_DECL_HTOBE32
+
+#if HAVE_DECL_HTOLE32 == 0
+inline uint32_t htole32(uint32_t host_32bits)
+{
+    return bswap_32(host_32bits);
+}
+#endif // HAVE_DECL_HTOLE32
+
+#if HAVE_DECL_BE32TOH == 0
+inline uint32_t be32toh(uint32_t big_endian_32bits)
+{
+    return big_endian_32bits;
+}
+#endif // HAVE_DECL_BE32TOH
+
+#if HAVE_DECL_LE32TOH == 0
+inline uint32_t le32toh(uint32_t little_endian_32bits)
+{
+    return bswap_32(little_endian_32bits);
+}
+#endif // HAVE_DECL_LE32TOH
+
+#if HAVE_DECL_HTOBE64 == 0
+inline uint64_t htobe64(uint64_t host_64bits)
+{
+    return host_64bits;
+}
+#endif // HAVE_DECL_HTOBE64
+
+#if HAVE_DECL_HTOLE64 == 0
+inline uint64_t htole64(uint64_t host_64bits)
+{
+    return bswap_64(host_64bits);
+}
+#endif // HAVE_DECL_HTOLE64
+
+#if HAVE_DECL_BE64TOH == 0
+inline uint64_t be64toh(uint64_t big_endian_64bits)
+{
+    return big_endian_64bits;
+}
+#endif // HAVE_DECL_BE64TOH
+
+#if HAVE_DECL_LE64TOH == 0
+inline uint64_t le64toh(uint64_t little_endian_64bits)
+{
+    return bswap_64(little_endian_64bits);
+}
+#endif // HAVE_DECL_LE64TOH
+
+#else // WORDS_BIGENDIAN
+
+#if HAVE_DECL_HTOBE16 == 0
+inline uint16_t htobe16(uint16_t host_16bits)
+{
+    return bswap_16(host_16bits);
+}
+#endif // HAVE_DECL_HTOBE16
+
+#if HAVE_DECL_HTOLE16 == 0
+inline uint16_t htole16(uint16_t host_16bits)
+{
+    return host_16bits;
+}
+#endif // HAVE_DECL_HTOLE16
+
+#if HAVE_DECL_BE16TOH == 0
+inline uint16_t be16toh(uint16_t big_endian_16bits)
+{
+    return bswap_16(big_endian_16bits);
+}
+#endif // HAVE_DECL_BE16TOH
+
+#if HAVE_DECL_LE16TOH == 0
+inline uint16_t le16toh(uint16_t little_endian_16bits)
+{
+    return little_endian_16bits;
+}
+#endif // HAVE_DECL_LE16TOH
+
+#if HAVE_DECL_HTOBE32 == 0
+inline uint32_t htobe32(uint32_t host_32bits)
+{
+    return bswap_32(host_32bits);
+}
+#endif // HAVE_DECL_HTOBE32
+
+#if HAVE_DECL_HTOLE32 == 0
+inline uint32_t htole32(uint32_t host_32bits)
+{
+    return host_32bits;
+}
+#endif // HAVE_DECL_HTOLE32
+
+#if HAVE_DECL_BE32TOH == 0
+inline uint32_t be32toh(uint32_t big_endian_32bits)
+{
+    return bswap_32(big_endian_32bits);
+}
+#endif // HAVE_DECL_BE32TOH
+
+#if HAVE_DECL_LE32TOH == 0
+inline uint32_t le32toh(uint32_t little_endian_32bits)
+{
+    return little_endian_32bits;
+}
+#endif // HAVE_DECL_LE32TOH
+
+#if HAVE_DECL_HTOBE64 == 0
+inline uint64_t htobe64(uint64_t host_64bits)
+{
+    return bswap_64(host_64bits);
+}
+#endif // HAVE_DECL_HTOBE64
+
+#if HAVE_DECL_HTOLE64 == 0
+inline uint64_t htole64(uint64_t host_64bits)
+{
+    return host_64bits;
+}
+#endif // HAVE_DECL_HTOLE64
+
+#if HAVE_DECL_BE64TOH == 0
+inline uint64_t be64toh(uint64_t big_endian_64bits)
+{
+    return bswap_64(big_endian_64bits);
+}
+#endif // HAVE_DECL_BE64TOH
+
+#if HAVE_DECL_LE64TOH == 0
+inline uint64_t le64toh(uint64_t little_endian_64bits)
+{
+    return little_endian_64bits;
+}
+#endif // HAVE_DECL_LE64TOH
+
+#endif // WORDS_BIGENDIAN
+
+#endif // DIGIBYTE_COMPAT_ENDIAN_H

src/compat/glibc_compat.cpp

@@ -0,0 +1,63 @@
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2014-2020 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#if defined(HAVE_CONFIG_H)
+#include <config/vexta-config.h>
+#endif
+
+#include <cstddef>
+#include <cstdint>
+
+#if defined(__i386__) || defined(__arm__)
+
+extern "C" int64_t __udivmoddi4(uint64_t u, uint64_t v, uint64_t* rp);
+
+extern "C" int64_t __wrap___divmoddi4(int64_t u, int64_t v, int64_t* rp)
+{
+    int32_t c1 = 0, c2 = 0;
+    int64_t uu = u, vv = v;
+    int64_t w;
+    int64_t r;
+
+    if (uu < 0) {
+        c1 = ~c1, c2 = ~c2, uu = -uu;
+    }
+    if (vv < 0) {
+        c1 = ~c1, vv = -vv;
+    }
+
+    w = __udivmoddi4(uu, vv, (uint64_t*)&r);
+    if (c1)
+        w = -w;
+    if (c2)
+        r = -r;
+
+    *rp = r;
+    return w;
+}
+#endif
+
+extern "C" float log2f_old(float x);
+#ifdef __i386__
+__asm(".symver log2f_old,log2f@GLIBC_2.1");
+#elif defined(__amd64__)
+__asm(".symver log2f_old,log2f@GLIBC_2.2.5");
+#elif defined(__arm__)
+__asm(".symver log2f_old,log2f@GLIBC_2.4");
+#elif defined(__aarch64__)
+__asm(".symver log2f_old,log2f@GLIBC_2.17");
+#elif defined(__powerpc64__)
+#  ifdef WORDS_BIGENDIAN
+__asm(".symver log2f_old,log2f@GLIBC_2.3");
+#  else
+__asm(".symver log2f_old,log2f@GLIBC_2.17");
+#  endif
+#elif defined(__riscv)
+__asm(".symver log2f_old,log2f@GLIBC_2.27");
+#endif
+extern "C" float __wrap_log2f(float x)
+{
+    return log2f_old(x);
+}

src/compat/glibc_sanity.cpp

@@ -0,0 +1,69 @@
+// Copyright (c) 2009-2019 The Bitcoin Core developers
+// Copyright (c) 2014-2019 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#if defined(HAVE_CONFIG_H)
+#include <config/vexta-config.h>
+#endif
+
+#include <cstddef>
+
+#if defined(HAVE_SYS_SELECT_H)
+#include <sys/select.h>
+#endif
+
+extern "C" void* memcpy(void* a, const void* b, size_t c);
+void* memcpy_int(void* a, const void* b, size_t c)
+{
+    return memcpy(a, b, c);
+}
+
+namespace
+{
+// trigger: Use the memcpy_int wrapper which calls our internal memcpy.
+//   A direct call to memcpy may be optimized away by the compiler.
+// test: Fill an array with a sequence of integers. memcpy to a new empty array.
+//   Verify that the arrays are equal. Use an odd size to decrease the odds of
+//   the call being optimized away.
+template <unsigned int T>
+bool sanity_test_memcpy()
+{
+    unsigned int memcpy_test[T];
+    unsigned int memcpy_verify[T] = {};
+    for (unsigned int i = 0; i != T; ++i)
+        memcpy_test[i] = i;
+
+    memcpy_int(memcpy_verify, memcpy_test, sizeof(memcpy_test));
+
+    for (unsigned int i = 0; i != T; ++i) {
+        if (memcpy_verify[i] != i)
+            return false;
+    }
+    return true;
+}
+
+#if defined(HAVE_SYS_SELECT_H)
+// trigger: Call FD_SET to trigger __fdelt_chk. FORTIFY_SOURCE must be defined
+//   as >0 and optimizations must be set to at least -O2.
+// test: Add a file descriptor to an empty fd_set. Verify that it has been
+//   correctly added.
+bool sanity_test_fdelt()
+{
+    fd_set fds;
+    FD_ZERO(&fds);
+    FD_SET(0, &fds);
+    return FD_ISSET(0, &fds);
+}
+#endif
+
+} // namespace
+
+bool glibc_sanity_test()
+{
+#if defined(HAVE_SYS_SELECT_H)
+    if (!sanity_test_fdelt())
+        return false;
+#endif
+    return sanity_test_memcpy<1025>();
+}

src/compat/glibcxx_sanity.cpp

@@ -0,0 +1,62 @@
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2014-2020 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <list>
+#include <locale>
+#include <stdexcept>
+
+namespace
+{
+// trigger: use ctype<char>::widen to trigger ctype<char>::_M_widen_init().
+// test: convert a char from narrow to wide and back. Verify that the result
+//   matches the original.
+bool sanity_test_widen(char testchar)
+{
+    const std::ctype<char>& test(std::use_facet<std::ctype<char> >(std::locale()));
+    return test.narrow(test.widen(testchar), 'b') == testchar;
+}
+
+// trigger: use list::push_back and list::pop_back to trigger _M_hook and
+//   _M_unhook.
+// test: Push a sequence of integers into a list. Pop them off and verify that
+//   they match the original sequence.
+bool sanity_test_list(unsigned int size)
+{
+    std::list<unsigned int> test;
+    for (unsigned int i = 0; i != size; ++i)
+        test.push_back(i + 1);
+
+    if (test.size() != size)
+        return false;
+
+    while (!test.empty()) {
+        if (test.back() != test.size())
+            return false;
+        test.pop_back();
+    }
+    return true;
+}
+
+} // namespace
+
+// trigger: string::at(x) on an empty string to trigger __throw_out_of_range_fmt.
+// test: force std::string to throw an out_of_range exception. Verify that
+//   it's caught correctly.
+bool sanity_test_range_fmt()
+{
+    std::string test;
+    try {
+        test.at(1);
+    } catch (const std::out_of_range&) {
+        return true;
+    } catch (...) {
+    }
+    return false;
+}
+
+bool glibcxx_sanity_test()
+{
+    return sanity_test_widen('a') && sanity_test_list(100) && sanity_test_range_fmt();
+}

src/compat/sanity.h

@@ -0,0 +1,10 @@
+// Copyright (c) 2009-2014 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef DIGIBYTE_COMPAT_SANITY_H
+#define DIGIBYTE_COMPAT_SANITY_H
+
+bool glibcxx_sanity_test();
+
+#endif // DIGIBYTE_COMPAT_SANITY_H

src/compat/stdin.cpp

@@ -0,0 +1,72 @@
+// Copyright (c) 2018-2019 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#if defined(HAVE_CONFIG_H)
+#include <config/vexta-config.h>
+#endif
+
+#include <cstdio>       // for fileno(), stdin
+
+#ifdef WIN32
+#include <windows.h>    // for SetStdinEcho()
+#include <io.h>         // for isatty()
+#else
+#include <termios.h>    // for SetStdinEcho()
+#include <unistd.h>     // for SetStdinEcho(), isatty()
+#include <poll.h>       // for StdinReady()
+#endif
+
+#include <compat/stdin.h>
+
+// https://stackoverflow.com/questions/1413445/reading-a-password-from-stdcin
+void SetStdinEcho(bool enable)
+{
+#ifdef WIN32
+    HANDLE hStdin = GetStdHandle(STD_INPUT_HANDLE);
+    DWORD mode;
+    GetConsoleMode(hStdin, &mode);
+    if (!enable) {
+        mode &= ~ENABLE_ECHO_INPUT;
+    } else {
+        mode |= ENABLE_ECHO_INPUT;
+    }
+    SetConsoleMode(hStdin, mode);
+#else
+    struct termios tty;
+    tcgetattr(STDIN_FILENO, &tty);
+    if (!enable) {
+        tty.c_lflag &= ~ECHO;
+    } else {
+        tty.c_lflag |= ECHO;
+    }
+    (void)tcsetattr(STDIN_FILENO, TCSANOW, &tty);
+#endif
+}
+
+bool StdinTerminal()
+{
+#ifdef WIN32
+    return _isatty(_fileno(stdin));
+#else
+    return isatty(fileno(stdin));
+#endif
+}
+
+bool StdinReady()
+{
+    if (!StdinTerminal()) {
+        return true;
+    }
+#ifdef WIN32
+    return false;
+#else
+    struct pollfd fds;
+    fds.fd = 0; /* this is STDIN */
+    fds.events = POLLIN;
+    return poll(&fds, 1, 0) == 1;
+#endif
+}
+
+NoechoInst::NoechoInst() { SetStdinEcho(false); }
+NoechoInst::~NoechoInst() { SetStdinEcho(true); }

src/compat/stdin.h

@@ -0,0 +1,18 @@
+// Copyright (c) 2018 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef DIGIBYTE_COMPAT_STDIN_H
+#define DIGIBYTE_COMPAT_STDIN_H
+
+struct NoechoInst {
+    NoechoInst();
+    ~NoechoInst();
+};
+
+#define NO_STDIN_ECHO() NoechoInst _no_echo
+
+bool StdinTerminal();
+bool StdinReady();
+
+#endif // DIGIBYTE_COMPAT_STDIN_H

src/compat/strnlen.cpp

@@ -0,0 +1,19 @@
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Copyright (c) 2014-2020 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#if defined(HAVE_CONFIG_H)
+#include <config/vexta-config.h>
+#endif
+
+#include <cstring>
+
+#if HAVE_DECL_STRNLEN == 0
+size_t strnlen( const char *start, size_t max_len)
+{
+    const char *end = (const char *)memchr(start, '\0', max_len);
+
+    return end ? (size_t)(end - start) : max_len;
+}
+#endif // HAVE_DECL_STRNLEN