jeanlemotan
108 lines
4.5 KiB
HTML
108 lines
4.5 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head>
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<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
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<Title>EAByteCrackers</title>
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<link type="text/css" rel="stylesheet" href="UTFDoc.css">
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<meta name="author" content="Paul Pedriana">
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</head>
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<body bgcolor="#FFFFFF">
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<h1>EAByteCrackers</h1>
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<h2>Introduction</h2>
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<p>EAByteCrackers is a small utility header file that provides macros for breaking down integers into component bytes and for building up integers from component
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bytes. These are particularly useful because working with signed values creates opportunities for mistakes, and the macros present in EAByteCrackers remove such
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possibilities for error. You can run into this need for dealing with signed values when working with Windows "winproc" message packing, for example.</p>
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<h2>Conventions</h2>
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<p>Components within an integer are numbered 0-N with 0 referring to the least significant component. Thus, the 32 bit value 0x12345678 consists of byte 0 = 0x78,
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byte 1 = 0x56, byte 2 = 0x34, and byte 3 = 0x12. This is done like so because the index of the byte is thus equal to its numerical shift within the integer. It
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also means that byte 2 of a uint32_t refers to the same value as byte 2 of a uint64_t. For example:</p>
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<pre class="code-example">uint16_t u16 = UINT16_5_FROM_UINT64(0x887766554433221100); <font color="#0066FF">// u16 becomes 0x55</font></pre>
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<p>Similarly, we have this:</p>
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<pre class="code-example">uint32_t u32 = UINT32_FROM_UINT8(0x33, 0x22, 0x11, 0x00); <font color="#0066FF">// u32 becomes 0x33221100</font></pre>
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<p>In the macros, the terms b, w, d, and q are used.</p>
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<ul>
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<li>b means 8 bit byte</li>
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<li>w means 16 bit word</li>
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<li>d means 32 bit dword</li>
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<li>q means 64 bit quadword</li>
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</ul>
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<h2>Example usage </h2>
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<p>Basic usage:</p>
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<pre class="code-example">// Integer breakdown
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uint8_t u8 = UINT8_0_FROM_UINT16(0x1100); <font color="#0066FF">// u8 becomes 0x00</font>
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uint8_t u8 = UINT8_2_FROM_UINT64(0x7766554433221100); <font color="#0066FF">// u8 becomes 0x22</font>
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uint16_t u16 = UINT16_3_FROM_UINT64(0x7766554433221100); <font color="#0066FF">// u16 becomes 0x7766</font>
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// Integer build up
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uint16_t u16 = UINT16_FROM_UINT8(0x11, 0x00); <font color="#0066FF">// u16 becomes 0x1100</font>
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uint32_t u32 = UINT32_FROM_UINT8(0x33, 0x22, 0x11, 0x00); <font color="#0066FF">// u32 becomes 0x33221100</font></pre>
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<p></p>
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<p>How to safely convert a 32 bit value to two signed 16 bit values:</p>
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<pre class="code-example">int16_t n0 = (int16_t)UINT16_0_FROM_UINT32(0x1000ffff); <font color="#0066FF">// n0 becomes -1</font>
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int16_t n1 = (int16_t)UINT16_1_FROM_UINT32(0x1000ffff); <font color="#0066FF">// n1 becomes 4096</font></pre>
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<p>How to build up a uint64_t from a uint32_t and two uint16_t values:</p>
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<pre class="code-example">uint64_t u64 = UINT64_FROM_UINT32(0x77665544, UINT32_FROM_UINT16(0x3322, 0x1100)); <font color="#0066FF">// u64 becomes 0x7766554433221100</font>
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</pre>
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<h2>Interface</h2>
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<pre class="code-example"><span class="code-example-comment">// uint8_t byte manipulators</span>
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#define UINT8_0_FROM_UINT16(w)
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#define UINT8_1_FROM_UINT16(w)
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#define UINT8_0_FROM_UINT32(d)
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#define UINT8_1_FROM_UINT32(d)
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#define UINT8_2_FROM_UINT32(d)
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#define UINT8_3_FROM_UINT32(d)
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#define UINT8_0_FROM_UINT64(q)
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#define UINT8_1_FROM_UINT64(q)
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#define UINT8_2_FROM_UINT64(q)
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#define UINT8_3_FROM_UINT64(q)
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#define UINT8_4_FROM_UINT64(q)
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#define UINT8_5_FROM_UINT64(q)
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#define UINT8_6_FROM_UINT64(q)
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#define UINT8_7_FROM_UINT64(q)
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<span class="code-example-comment">// uint16_t byte manipulators</span>
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#define UINT16_0_FROM_UINT32(d)
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#define UINT16_1_FROM_UINT32(d)
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#define UINT16_0_FROM_UINT64(q)
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#define UINT16_1_FROM_UINT64(q)
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#define UINT16_2_FROM_UINT64(q)
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#define UINT16_3_FROM_UINT64(q)
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#define UINT16_FROM_UINT8(b1, b0)
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<span class="code-example-comment">// uint32_t byte manipulators</span>
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#define UINT32_2_FROM_UINT64(q)
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#define UINT32_1_FROM_UINT64(q)
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#define UINT32_FROM_UINT8(b3, b2, b1, b0)
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#define UINT32_FROM_UINT16(w1, w0)
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<span class="code-example-comment">// uint64_t byte manipulators</span>
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#define UINT64_FROM_UINT8(b7, b6, b5, b4, b3, b2, b1, b0)
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#define UINT64_FROM_UINT16(w3, w2, w1, w0)
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#define UINT64_FROM_UINT32(d1, d0)
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</pre>
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<p></p>
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<hr>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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<p> </p>
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</body></html>
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