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NetIF_GetTxDataAlignPtr()
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Files
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net_if.h/net_if.cPrototype
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| rowspan | 3 |
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Arguments
if_nbr
Network interface number to get a transmit application buffer's aligned data pointer.
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p_dataPointer to transmit application data buffer to get an aligned pointer into (see also Note #2b).
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perrPointer to variable that will receive the return error code from this function :
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NET_IF_ERR_NONE
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NET_IF_ERR_NULL_PTR
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NET_IF_ERR_INVALID_IF
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NET_IF_ERR_ALIGN_NOT_AVAIL
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NET_ERR_INIT_INCOMPLETE
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NET_ERR_INVALID_TRANSACTION
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NET_OS_ERR_LOCK
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Returned Value
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Pointer to aligned transmit application data buffer address, if no errors.Anchor
Pointer to NULL, otherwise.Anchor
Required Configuration
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None.Anchor
Notes/Warnings #1
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Otherwise, a single, fixed alignment between application data buffers and network interface's buffer data areas is not possible.
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For any single read/write of data to/from application data buffers and network buffer data areas, optimal alignment occurs if, and only if, all of the following conditions are true:
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In other words, the modulus of the specific read/write address in the application data buffer with the CPU's data word size must be equal to the modulus of the specific read/write address in the network buffer data area with the CPU's data word size.
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This condition might not be satisfied whenever:
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However, even though optimal alignment between application data buffers and network buffer data areas is not guaranteed for every read/write; optimal alignment should not occur more frequently, leading to improved network data throughput.
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Notes/Warnings #2
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Since the first aligned address in the application data buffer may be 0 to (CPU_CFG_DATA_SIZE-1) bytes after the application data buffer's starting address, the application data buffer should allocate and reserve an additional (CPU_CFG_DATA_SIZE-1) number of bytes.Anchor
However, the application data buffer's effective, useable size is still limited to its original declared size (before reserving additional bytes), and should not be increased by the additional, reserved bytes.