1BIO_S_MEM(3)                        OpenSSL                       BIO_S_MEM(3)
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NAME

6       BIO_s_secmem, BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data,
7       BIO_set_mem_buf, BIO_get_mem_ptr, BIO_new_mem_buf - memory BIO
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SYNOPSIS

10        #include <openssl/bio.h>
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12        const BIO_METHOD *BIO_s_mem(void);
13        const BIO_METHOD *BIO_s_secmem(void);
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15        BIO_set_mem_eof_return(BIO *b, int v)
16        long BIO_get_mem_data(BIO *b, char **pp)
17        BIO_set_mem_buf(BIO *b, BUF_MEM *bm, int c)
18        BIO_get_mem_ptr(BIO *b, BUF_MEM **pp)
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20        BIO *BIO_new_mem_buf(const void *buf, int len);
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DESCRIPTION

23       BIO_s_mem() returns the memory BIO method function.
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25       A memory BIO is a source/sink BIO which uses memory for its I/O. Data
26       written to a memory BIO is stored in a BUF_MEM structure which is
27       extended as appropriate to accommodate the stored data.
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29       BIO_s_secmem() is like BIO_s_mem() except that the secure heap is used
30       for buffer storage.
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32       Any data written to a memory BIO can be recalled by reading from it.
33       Unless the memory BIO is read only any data read from it is deleted
34       from the BIO.
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36       Memory BIOs support BIO_gets() and BIO_puts().
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38       If the BIO_CLOSE flag is set when a memory BIO is freed then the
39       underlying BUF_MEM structure is also freed.
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41       Calling BIO_reset() on a read write memory BIO clears any data in it if
42       the flag BIO_FLAGS_NONCLEAR_RST is not set. On a read only BIO or if
43       the flag BIO_FLAGS_NONCLEAR_RST is set it restores the BIO to its
44       original state and the data can be read again.
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46       BIO_eof() is true if no data is in the BIO.
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48       BIO_ctrl_pending() returns the number of bytes currently stored.
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50       BIO_set_mem_eof_return() sets the behaviour of memory BIO b when it is
51       empty. If the v is zero then an empty memory BIO will return EOF (that
52       is it will return zero and BIO_should_retry(b) will be false. If v is
53       non zero then it will return v when it is empty and it will set the
54       read retry flag (that is BIO_read_retry(b) is true). To avoid ambiguity
55       with a normal positive return value v should be set to a negative
56       value, typically -1.
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58       BIO_get_mem_data() sets *pp to a pointer to the start of the memory
59       BIOs data and returns the total amount of data available. It is
60       implemented as a macro.
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62       BIO_set_mem_buf() sets the internal BUF_MEM structure to bm and sets
63       the close flag to c, that is c should be either BIO_CLOSE or
64       BIO_NOCLOSE.  It is a macro.
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66       BIO_get_mem_ptr() places the underlying BUF_MEM structure in *pp. It is
67       a macro.
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69       BIO_new_mem_buf() creates a memory BIO using len bytes of data at buf,
70       if len is -1 then the buf is assumed to be nul terminated and its
71       length is determined by strlen. The BIO is set to a read only state and
72       as a result cannot be written to. This is useful when some data needs
73       to be made available from a static area of memory in the form of a BIO.
74       The supplied data is read directly from the supplied buffer: it is not
75       copied first, so the supplied area of memory must be unchanged until
76       the BIO is freed.
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NOTES

79       Writes to memory BIOs will always succeed if memory is available: that
80       is their size can grow indefinitely.
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82       Every read from a read write memory BIO will remove the data just read
83       with an internal copy operation, if a BIO contains a lot of data and it
84       is read in small chunks the operation can be very slow. The use of a
85       read only memory BIO avoids this problem. If the BIO must be read write
86       then adding a buffering BIO to the chain will speed up the process.
87
88       Calling BIO_set_mem_buf() on a BIO created with BIO_new_secmem() will
89       give undefined results, including perhaps a program crash.
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BUGS

92       There should be an option to set the maximum size of a memory BIO.
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EXAMPLE

95       Create a memory BIO and write some data to it:
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97        BIO *mem = BIO_new(BIO_s_mem());
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99        BIO_puts(mem, "Hello World\n");
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101       Create a read only memory BIO:
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103        char data[] = "Hello World";
104        BIO *mem = BIO_new_mem_buf(data, -1);
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106       Extract the BUF_MEM structure from a memory BIO and then free up the
107       BIO:
108
109        BUF_MEM *bptr;
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111        BIO_get_mem_ptr(mem, &bptr);
112        BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */
113        BIO_free(mem);
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RETURN VALUES

116       BIO_s_mem() and BIO_s_secmem() return a valid memory BIO_METHOD
117       structure.
118
119       BIO_set_mem_eof_return(), BIO_get_mem_data(), BIO_set_mem_buf() and
120       BIO_get_mem_ptr() return 1 on success or a value which is less than or
121       equal to 0 if an error occurred.
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123       BIO_new_mem_buf() returns a valid BIO structure on success or NULL on
124       error.
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127       Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
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129       Licensed under the OpenSSL license (the "License").  You may not use
130       this file except in compliance with the License.  You can obtain a copy
131       in the file LICENSE in the source distribution or at
132       <https://www.openssl.org/source/license.html>.
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1361.1.1                             2018-09-11                      BIO_S_MEM(3)
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