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| 1 | .Dd $Mdocdate: February 16 2015 $ | ||
| 2 | .Dt BIO_PUSH 3 | ||
| 3 | .Os | ||
| 4 | .Sh NAME | ||
| 5 | .Nm BIO_push , | ||
| 6 | .Nm BIO_pop | ||
| 7 | .Nd add and remove BIOs from a chain | ||
| 8 | .Sh SYNOPSIS | ||
| 9 | .In openssl/bio.h | ||
| 10 | .Ft BIO * | ||
| 11 | .Fo BIO_push | ||
| 12 | .Fa "BIO *b" | ||
| 13 | .Fa "BIO *append" | ||
| 14 | .Fc | ||
| 15 | .Ft BIO * | ||
| 16 | .Fo BIO_pop | ||
| 17 | .Fa "BIO *b" | ||
| 18 | .Fc | ||
| 19 | .Sh DESCRIPTION | ||
| 20 | The | ||
| 21 | .Fn BIO_push | ||
| 22 | function appends the BIO | ||
| 23 | .Fa append | ||
| 24 | to | ||
| 25 | .Fa b | ||
| 26 | and returns | ||
| 27 | .Fa b . | ||
| 28 | .Pp | ||
| 29 | .Fn BIO_pop | ||
| 30 | removes the BIO | ||
| 31 | .Fa b | ||
| 32 | from a chain and returns the next BIO in the chain, or | ||
| 33 | .Dv NULL | ||
| 34 | if there is no next BIO. | ||
| 35 | The removed BIO then becomes a single BIO with no association with the | ||
| 36 | original chain, it can thus be freed or attached to a different chain. | ||
| 37 | .Sh RETURN VALUES | ||
| 38 | .Fn BIO_push | ||
| 39 | returns the beginning of the chain, | ||
| 40 | .Fa b . | ||
| 41 | .Pp | ||
| 42 | .Fn BIO_pop | ||
| 43 | returns the next BIO in the chain, or | ||
| 44 | .Dv NULL | ||
| 45 | if there is no next BIO. | ||
| 46 | .Sh NOTES | ||
| 47 | The names of these functions are perhaps a little misleading. | ||
| 48 | .Fn BIO_push | ||
| 49 | joins two BIO chains whereas | ||
| 50 | .Fn BIO_pop | ||
| 51 | deletes a single BIO from a chain, | ||
| 52 | the deleted BIO does not need to be at the end of a chain. | ||
| 53 | .Pp | ||
| 54 | The process of calling | ||
| 55 | .Fn BIO_push | ||
| 56 | and | ||
| 57 | .Fn BIO_pop | ||
| 58 | on a BIO may have additional consequences: | ||
| 59 | a control call is made to the affected BIOs. | ||
| 60 | Any effects will be noted in the descriptions of individual BIOs. | ||
| 61 | .Sh EXAMPLES | ||
| 62 | For these examples suppose | ||
| 63 | .Sy md1 | ||
| 64 | and | ||
| 65 | .Sy md2 | ||
| 66 | are digest BIOs, | ||
| 67 | .Sy b64 | ||
| 68 | is a base64 BIO and | ||
| 69 | .Sy f | ||
| 70 | is a file BIO. | ||
| 71 | .Pp | ||
| 72 | If the call | ||
| 73 | .Pp | ||
| 74 | .Dl BIO_push(b64, f); | ||
| 75 | .Pp | ||
| 76 | is made then the new chain will be | ||
| 77 | .Sy b64-f . | ||
| 78 | After making the calls | ||
| 79 | .Bd -literal -offset indent | ||
| 80 | BIO_push(md2, b64); | ||
| 81 | BIO_push(md1, md2); | ||
| 82 | .Ed | ||
| 83 | .Pp | ||
| 84 | the new chain is | ||
| 85 | .Sy md1-md2-b64-f . | ||
| 86 | Data written to | ||
| 87 | .Sy md1 | ||
| 88 | will be digested | ||
| 89 | by | ||
| 90 | .Sy md1 | ||
| 91 | and | ||
| 92 | .Sy md2 , | ||
| 93 | .Sy base64 | ||
| 94 | encoded and written to | ||
| 95 | .Sy f . | ||
| 96 | .Pp | ||
| 97 | It should be noted that reading causes data to pass | ||
| 98 | in the reverse direction, that is data is read from | ||
| 99 | .Sy f , | ||
| 100 | base64 | ||
| 101 | .Sy decoded | ||
| 102 | and digested | ||
| 103 | by | ||
| 104 | .Sy md1 | ||
| 105 | and | ||
| 106 | .Sy md2 . | ||
| 107 | If this call is made: | ||
| 108 | .Pp | ||
| 109 | .Dl BIO_pop(md2); | ||
| 110 | .Pp | ||
| 111 | The call will return | ||
| 112 | .Sy b64 | ||
| 113 | and the new chain will be | ||
| 114 | .Sy md1-b64-f Ns ; | ||
| 115 | data can be written to | ||
| 116 | .Sy md1 | ||
| 117 | as before. | ||