import itoa_ljust.c for fast number printing

converted from C++. for best speed, needs to be built with O3

1 files changed, 149 insertions, 0 deletions

diff --git a/itoa_ljust.c b/itoa_ljust.c
new file mode 100644
index 0000000..4ed9267
--- /dev/null
+++ b/itoa_ljust.c
@@ -0,0 +1,149 @@
+//=== itoa_ljust.cpp - Fast integer to ascii conversion           --*- C++ -*-//
+//
+// Substantially simplified (and slightly faster) version
+// based on the following functions in Google's protocol buffers:
+//
+//    FastInt32ToBufferLeft()
+//    FastUInt32ToBufferLeft()
+//    FastInt64ToBufferLeft()
+//    FastUInt64ToBufferLeft()
+//
+// Differences:
+//    1) Greatly simplified
+//    2) Avoids GOTO statements - uses "switch" instead and relies on
+//       compiler constant folding and propagation for high performance
+//    3) Avoids unary minus of signed types - undefined behavior if value
+//       is INT_MIN in platforms using two's complement representation
+//    4) Uses memcpy to store 2 digits at a time - lets the compiler
+//       generate a 2-byte load/store in platforms that support
+//       unaligned access, this is faster (and less code) than explicitly
+//       loading and storing each byte
+//
+// Copyright (c) 2016 Arturo Martin-de-Nicolas
+// arturomdn@gmail.com
+// https://github.com/amdn/itoa_ljust/
+//
+// Released under the BSD 3-Clause License, see Google's original copyright
+// and license below.
+//===----------------------------------------------------------------------===//
+
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//===----------------------------------------------------------------------===//
+
+#include "itoa_ljust.h"
+#include <string.h>
+
+static const char lut[201] =
+    "0001020304050607080910111213141516171819"
+    "2021222324252627282930313233343536373839"
+    "4041424344454647484950515253545556575859"
+    "6061626364656667686970717273747576777879"
+    "8081828384858687888990919293949596979899";
+
+#define dd(u) ((const uint16_t)(lut[u]))
+
+static inline char* out2(const int d, char* p) {
+    memcpy(p, &((uint16_t *)lut)[d], 2);
+    return p + 2;
+}
+
+static inline char* out1(const char in, char* p) {
+    memcpy(p, &in, 1);
+    return p + 1;
+}
+
+static inline int digits( uint32_t u, unsigned k, int* d, char** p, int n ) {
+    if (u < k*10) {
+        *d = u / k;
+        *p = out1('0'+*d, *p);
+        --n;
+    }
+    return n;
+}
+
+static inline char* itoa(uint32_t u, char* p, int d, int n) {
+    switch(n) {
+    case 10: d  = u / 100000000; p = out2( d, p );
+    case  9: u -= d * 100000000;
+    case  8: d  = u /   1000000; p = out2( d, p );
+    case  7: u -= d *   1000000;
+    case  6: d  = u /     10000; p = out2( d, p );
+    case  5: u -= d *     10000;
+    case  4: d  = u /       100; p = out2( d, p );
+    case  3: u -= d *       100;
+    case  2: d  = u /         1; p = out2( d, p );
+    case  1: ;
+    }
+    *p = '\0';
+    return p;
+}
+
+char* itoa_u32(uint32_t u, char* p) {
+    int d,n;
+         if (u >=100000000) n = digits(u, 100000000, &d, &p, 10);
+    else if (u <       100) n = digits(u,         1, &d, &p,  2);
+    else if (u <     10000) n = digits(u,       100, &d, &p,  4);
+    else if (u <   1000000) n = digits(u,     10000, &d, &p,  6);
+    else                    n = digits(u,   1000000, &d, &p,  8);
+    return itoa( u, p, d, n );
+}
+
+char* itoa_32(int32_t i, char* p) {
+    uint32_t u = i;
+    if (i < 0) {
+        *p++ = '-';
+        u = -u;
+    }
+    return itoa_u32(u, p);
+}
+
+char* itoa_u64(uint64_t u, char* p) {
+    int d;
+
+    uint32_t lower = (uint32_t)u;
+    if (lower == u) return itoa_u32(lower, p);
+
+    uint64_t upper = u / 1000000000;
+    p = itoa_u64(upper, p);
+    lower = u - (upper * 1000000000);
+    d = lower / 100000000;
+    p = out1('0'+d,p);
+    return itoa( lower, p, d, 9 );
+}
+
+char* itoa_64(int64_t i, char* p) {
+    uint64_t u = i;
+    if (i < 0) {
+        *p++ = '-';
+        u = -u;
+    }
+    return itoa_u64(u, p);
+}