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22 lines
1.2 KiB
C
22 lines
1.2 KiB
C
#ifndef INTOVERFLOW_H
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#define INTOVERFLOW_H
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// simple safe library to handle integer overflows when doing buffer size calculations
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// Usage:
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// - calculate data size using INTOVERFLOW_??? macros
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// - compare: calculated-size <= INTOVERFLOW_NORMALIZE(buffersize)
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// Functionality:
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// - all overflows (values > INTOVERFLOW_MAX) and errors are mapped to INTOVERFLOW_MAX
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// - if any input of an operation is INTOVERFLOW_MAX, INTOVERFLOW_MAX will be returned
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// - otherwise, regular arithmetics apply
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#define INTOVERFLOW_MAX 2147483647
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#define INTOVERFLOW_ADD(a,b) (((a) < INTOVERFLOW_MAX && (b) < INTOVERFLOW_MAX && (a) < INTOVERFLOW_MAX - (b)) ? ((a) + (b)) : INTOVERFLOW_MAX)
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#define INTOVERFLOW_SUB(a,b) (((a) < INTOVERFLOW_MAX && (b) < INTOVERFLOW_MAX && (b) <= (a)) ? ((a) - (b)) : INTOVERFLOW_MAX)
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#define INTOVERFLOW_MUL(a,b) (((a) < INTOVERFLOW_MAX && (b) < INTOVERFLOW_MAX && (a) < INTOVERFLOW_MAX / (b)) ? ((a) * (b)) : INTOVERFLOW_MAX)
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#define INTOVERFLOW_DIV(a,b) (((a) < INTOVERFLOW_MAX && (b) < INTOVERFLOW_MAX && (b) > 0) ? ((a) / (b)) : INTOVERFLOW_MAX)
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#define INTOVERFLOW_NORMALIZE(a) (((a) < INTOVERFLOW_MAX) ? (a) : (INTOVERFLOW_MAX - 1))
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#endif
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