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1 /* go-strslice.c -- the go string slice function.
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2
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3 Copyright 2009 The Go Authors. All rights reserved.
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4 Use of this source code is governed by a BSD-style
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5 license that can be found in the LICENSE file. */
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6
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7 #include "runtime.h"
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8
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9 String
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10 __go_string_slice (String s, intgo start, intgo end)
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11 {
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12 intgo len;
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13 String ret;
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14
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15 len = s.len;
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16 if (end == -1)
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17 end = len;
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18 if (start > len || end < start || end > len)
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19 runtime_panicstring ("string index out of bounds");
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20 ret.len = end - start;
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21 // If the length of the new string is zero, the str field doesn't
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22 // matter, so just set it to nil. This avoids the problem of
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23 // s.str + start pointing just past the end of the string,
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24 // which may keep the next memory block alive unnecessarily.
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25 if (ret.len == 0)
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26 ret.str = nil;
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27 else
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28 ret.str = s.str + start;
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29 return ret;
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30 }
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