1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-0142B290-DA6C-5574-83D7-7555D804D9B5" xml:lang="en"><title>How |
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13 to initialise array RESOURCE members</title><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <p><i><codeph><array-initialiser></codeph></i> </p> |
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15 <p><b>array-initialiser ::=</b> </p> |
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16 <p><b> {</b> <i><codeph><array-initialiser-item-comma-list></codeph></i><b> }</b> <i><codeph><array-initialiser-item></codeph></i> </p> |
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17 <p><b>array-initialiser-item ::=</b> </p> |
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18 <p><codeph><i><initialiser></i></codeph></p> |
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19 <p><b>Fixed-length arrays</b> </p> |
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20 <p>If a member is declared as a fixed-length array in the <codeph>STRUCT</codeph> or <codeph>RESOURCE</codeph> definition, |
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21 for example,</p> |
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22 <codeblock id="GUID-B2D4E3E1-2F01-53A4-92AE-AB99E3D2A680" xml:space="preserve">WORD elements[10]</codeblock> |
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23 <p>then you must not specify any more items than were given in the length. </p> |
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24 <p>If fewer items are specified in the default initialisation (i.e. in the <codeph>STRUCT</codeph> definition), |
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25 then an error also results. </p> |
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26 <p>Note that no values will be given to unspecified elements at the end of |
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27 the array, even if they have been default initialised in the <codeph>STRUCT</codeph> definition. |
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28 Take the following example:</p> |
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29 <codeblock id="GUID-02A51707-F693-588B-9B84-35D5F04E26EB" xml:space="preserve">STRUCT SAMPLE |
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30 { |
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31 BYTE bts[3]={1,2,3}; |
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32 }</codeblock> |
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33 <p>In the following resource:</p> |
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34 <codeblock id="GUID-D1C8604D-6877-54EA-A880-14316BC11008" xml:space="preserve">RESOURCE SAMPLE default |
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35 {}</codeblock> |
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36 <p>the output will be the whole default array</p> |
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37 <codeblock id="GUID-6CA06CBD-03A3-5CA9-8E66-69E8F703470D" xml:space="preserve">0x01 0x02 0x03</codeblock> |
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38 <p>but in this resource:</p> |
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39 <codeblock id="GUID-4B3D2892-C408-547F-9D83-40963CF68D19" xml:space="preserve">RESOURCE SAMPLE first_specified |
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40 { |
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41 bts={5}; |
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42 }</codeblock> |
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43 <p>the output is:</p> |
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44 <codeblock id="GUID-DE3C3486-1084-5A69-8BAE-0DDC0975D8B6" xml:space="preserve">0x05</codeblock> |
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45 <p>with the second and third elements lost. </p> |
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46 <p>If you specify only the second element in the <codeph>RESOURCE</codeph> definition, |
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47 then the first element is taken from the default initialisation, the second |
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48 from the explicit initialisation and the third element is lost. The following |
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49 resource:</p> |
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50 <codeblock id="GUID-0A8BB7DF-64BC-5399-921C-82E304B0F58D" xml:space="preserve">RESOURCE SAMPLE second_specified |
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51 { |
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52 bts[1]=5; |
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53 }</codeblock> |
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54 <p>results in the 2-byte output:</p> |
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55 <codeblock id="GUID-90DEAE7C-41E3-5D14-B074-A9BDC3862363" xml:space="preserve">0x01 0x05</codeblock> |
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56 <p>If, however, you explicitly initialise an element in the middle of an array |
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57 without having supplied default values for array members before it, then an |
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58 error will result.</p> |
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59 <section><title>Using expressions to initialise array elements</title> <p>You |
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60 may initialise array elements with expressions. You must explicitly initialise |
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61 each member component of the array otherwise the expressions will be evaluated |
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62 incorrectly. The following resource:</p> <codeblock id="GUID-59A9B709-7E44-51BE-A690-7E126EBF4483" xml:space="preserve">RESOURCE SAMPLE correct_expression |
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63 { |
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64 bts[0]=3+1; |
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65 bts[1]=2; |
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66 bts[2]=3; |
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67 }</codeblock> <p>will generate the correct output <codeph>0x04 0x02 0x03</codeph>. |
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68 However, if you use the following syntax:</p> <codeblock id="GUID-943761CA-D4ED-5B8E-9997-17785E1881FB" xml:space="preserve">RESOURCE SAMPLE incorrect_expression |
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69 { |
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70 bts={3+1,2,3}; |
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71 }</codeblock> <p>the output will be <codeph>0x03 0x02 0x03</codeph>. This |
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72 is because the pre-processor treats <codeph>3+1</codeph> as a literal string |
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73 that is then interpreted by the compiler as 3. In the resource <codeph>correct_expression</codeph> above |
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74 the ‘=‘ sign forces the pre-processor to evaluate the expression.</p> </section> |
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75 </conbody></concept> |
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