1 | #include <assert.h> |
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2 | #include <windows.h> |
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3 | #include <process.h> |
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4 | |
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5 | /* Sbrk implementation for Win32 by Emery Berger, http://www.cs.utexas.edu/users/emery */ |
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6 | |
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7 | void * sbrk (long size) { |
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8 | |
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9 | /* Reserve up to 1 GB of RAM */ |
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10 | /* |
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11 | We pre-reserve a very large chunk of memory |
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12 | and commit pages as we go. */ |
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13 | |
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14 | #define PRE_RESERVE 1024 * 1024 * 1024 |
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15 | |
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16 | static long remainingReserved = PRE_RESERVE; |
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17 | |
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18 | static int initialized = 0; |
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19 | static char * currentPosition = NULL; |
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20 | static char * nextPage = NULL; |
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21 | static long remainingCommitted = 0; |
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22 | static long pageSize; |
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23 | void * p; |
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24 | |
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25 | if (!initialized) { |
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26 | |
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27 | /* |
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28 | Do one-time initialization stuff: |
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29 | get the page size from the system, |
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30 | reserve a large range of memory, |
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31 | and initialize the appropriate variables. |
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32 | |
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33 | */ |
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34 | |
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35 | SYSTEM_INFO sSysInfo; |
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36 | LPVOID base; |
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37 | GetSystemInfo(&sSysInfo); |
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38 | |
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39 | pageSize = sSysInfo.dwPageSize; |
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40 | |
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41 | /* Reserve pages in the process's virtual address space. */ |
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42 | |
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43 | #if 1 |
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44 | base = VirtualAlloc(NULL, remainingReserved, MEM_RESERVE, PAGE_NOACCESS); |
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45 | #else |
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46 | base = VirtualAlloc(NULL, remainingReserved, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE); |
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47 | remainingCommitted = PRE_RESERVE; |
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48 | #endif |
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49 | |
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50 | if (base == NULL ) |
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51 | exit (1); /* VirtualAlloc reserve failed */ |
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52 | |
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53 | currentPosition = nextPage = (char *) base; |
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54 | initialized = 1; |
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55 | } |
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56 | |
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57 | if (size < 0) { |
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58 | |
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59 | #if 0 |
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60 | /* Uncommit pages if possible. |
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61 | Round the size down to a multiple of the page size, |
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62 | and decommit those pages. |
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63 | */ |
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64 | |
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65 | |
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66 | int bytesToUncommit = (-size & ~(pageSize - 1)); |
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67 | |
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68 | if (bytesToUncommit > PRE_RESERVE - remainingReserved) { |
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69 | /* Error -- the user has tried to free memory that we never |
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70 | even reserved. */ |
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71 | return currentPosition; |
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72 | } |
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73 | |
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74 | if (bytesToUncommit > 0) { |
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75 | |
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76 | int result = VirtualFree (nextPage - bytesToUncommit, bytesToUncommit, MEM_DECOMMIT); |
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77 | if (result == 0) { |
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78 | /* Error -- don't change a thing. */ |
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79 | return currentPosition; |
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80 | } |
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81 | remainingCommitted -= bytesToUncommit; |
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82 | } |
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83 | |
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84 | currentPosition -= size; |
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85 | remainingReserved += size; |
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86 | #endif |
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87 | return currentPosition; |
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88 | |
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89 | } |
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90 | |
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91 | if (size > 0) { |
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92 | void * p; |
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93 | if (size > remainingCommitted) { |
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94 | |
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95 | /* Commit some more pages. |
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96 | We round up to an even number of pages. |
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97 | Note that page size must be a power of two. |
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98 | */ |
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99 | |
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100 | int bytesToCommit = (size - remainingCommitted + pageSize - 1) & ~(pageSize - 1); |
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101 | int * result; |
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102 | |
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103 | result = VirtualAlloc((LPVOID) nextPage, bytesToCommit, MEM_COMMIT, PAGE_EXECUTE_READWRITE); |
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104 | |
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105 | if (result == NULL ) |
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106 | exit (1); /* VirtualAlloc commit failed */ |
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107 | |
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108 | nextPage += bytesToCommit; |
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109 | remainingCommitted += bytesToCommit; |
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110 | } |
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111 | |
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112 | p = currentPosition; |
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113 | currentPosition += size; |
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114 | remainingCommitted -= size; |
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115 | remainingReserved -= size; |
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116 | return p; |
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117 | } |
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118 | |
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119 | assert (size == 0); |
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120 | return currentPosition; |
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121 | |
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122 | } |
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