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annotate nspr/pr/include/prenv.h @ 4:b513267f632f tip

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Build DBM module
author Andre Heinecke <andre.heinecke@intevation.de>
date Tue, 05 Aug 2014 18:58:03 +0200
parents 1e5118fa0cb1
children
rev   line source
0
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1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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2 /* This Source Code Form is subject to the terms of the Mozilla Public
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3 * License, v. 2.0. If a copy of the MPL was not distributed with this
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4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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5
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6 #ifndef prenv_h___
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7 #define prenv_h___
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8
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9 #include "prtypes.h"
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10
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11 /*******************************************************************************/
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12 /*******************************************************************************/
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13 /****************** THESE FUNCTIONS MAY NOT BE THREAD SAFE *********************/
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14 /*******************************************************************************/
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15 /*******************************************************************************/
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16
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17 PR_BEGIN_EXTERN_C
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18
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19 /*
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20 ** PR_GetEnv() -- Retrieve value of environment variable
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21 **
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22 ** Description:
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23 ** PR_GetEnv() is modeled on Unix getenv().
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24 **
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25 **
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26 ** Inputs:
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27 ** var -- The name of the environment variable
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28 **
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29 ** Returns:
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30 ** The value of the environment variable 'var' or NULL if
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31 ** the variable is undefined.
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32 **
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33 ** Restrictions:
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34 ** You'd think that a POSIX getenv(), putenv() would be
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35 ** consistently implemented everywhere. Surprise! It is not. On
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36 ** some platforms, a putenv() where the argument is of
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37 ** the form "name" causes the named environment variable to
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38 ** be un-set; that is: a subsequent getenv() returns NULL. On
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39 ** other platforms, the putenv() fails, on others, it is a
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40 ** no-op. Similarly, a putenv() where the argument is of the
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41 ** form "name=" causes the named environment variable to be
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42 ** un-set; a subsequent call to getenv() returns NULL. On
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43 ** other platforms, a subsequent call to getenv() returns a
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44 ** pointer to a null-string (a byte of zero).
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45 **
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46 ** PR_GetEnv(), PR_SetEnv() provide a consistent behavior
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47 ** across all supported platforms. There are, however, some
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48 ** restrictions and some practices you must use to achieve
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49 ** consistent results everywhere.
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50 **
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51 ** When manipulating the environment there is no way to un-set
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52 ** an environment variable across all platforms. We suggest
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53 ** you interpret the return of a pointer to null-string to
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54 ** mean the same as a return of NULL from PR_GetEnv().
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55 **
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56 ** A call to PR_SetEnv() where the parameter is of the form
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57 ** "name" will return PR_FAILURE; the environment remains
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58 ** unchanged. A call to PR_SetEnv() where the parameter is
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59 ** of the form "name=" may un-set the envrionment variable on
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60 ** some platforms; on others it may set the value of the
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61 ** environment variable to the null-string.
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62 **
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63 ** For example, to test for NULL return or return of the
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64 ** null-string from PR_GetEnv(), use the following code
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65 ** fragment:
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66 **
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67 ** char *val = PR_GetEnv("foo");
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68 ** if ((NULL == val) || ('\0' == *val)) {
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69 ** ... interpret this as un-set ...
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70 ** }
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71 **
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72 ** The caller must ensure that the string passed
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73 ** to PR_SetEnv() is persistent. That is: The string should
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74 ** not be on the stack, where it can be overwritten
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75 ** on return from the function calling PR_SetEnv().
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76 ** Similarly, the string passed to PR_SetEnv() must not be
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77 ** overwritten by other actions of the process. ... Some
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78 ** platforms use the string by reference rather than copying
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79 ** it into the environment space. ... You have been warned!
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80 **
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81 ** Use of platform-native functions that manipulate the
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82 ** environment (getenv(), putenv(),
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83 ** SetEnvironmentVariable(), etc.) must not be used with
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84 ** NSPR's similar functions. The platform-native functions
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85 ** may not be thread safe and/or may operate on different
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86 ** conceptual environment space than that operated upon by
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87 ** NSPR's functions or other environment manipulating
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88 ** functions on the same platform. (!)
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89 **
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90 */
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91 NSPR_API(char*) PR_GetEnv(const char *var);
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92
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93 /*
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94 ** PR_SetEnv() -- set, unset or change an environment variable
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95 **
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96 ** Description:
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97 ** PR_SetEnv() is modeled on the Unix putenv() function.
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98 **
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99 ** Inputs:
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100 ** string -- pointer to a caller supplied
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101 ** constant, persistent string of the form name=value. Where
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102 ** name is the name of the environment variable to be set or
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103 ** changed; value is the value assigned to the variable.
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104 **
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105 ** Returns:
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106 ** PRStatus.
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107 **
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108 ** Restrictions:
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109 ** See the Restrictions documented in the description of
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110 ** PR_GetEnv() in this header file.
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111 **
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112 **
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113 */
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114 NSPR_API(PRStatus) PR_SetEnv(const char *string);
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115
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116 PR_END_EXTERN_C
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117
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118 #endif /* prenv_h___ */
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