54 lines
1.6 KiB
Markdown
54 lines
1.6 KiB
Markdown
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# Civetweb API Reference
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### `mg_read( conn, buf, len );`
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### Parameters
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| Parameter | Type | Description |
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| :--- | :--- | :--- |
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|**`conn`**|`struct mg_connection *`| A pointer referencing the connection |
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|**`buf`**|`void *`| A pointer to the location where the received data can be stored |
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|**`len`**|`size_t`| The maximum number of bytes to be stored in the buffer |
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### Return Value
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| Type | Description |
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| :--- | :--- |
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|`int`| The number of read bytes, or a status indication |
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### Description
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The function `mg_read()` receives data over an existing connection. The data is handled as binary and is stored in a buffer whose address has been provided as a parameter. The function returns the number of read bytes when successful, the value **0** when the connection has been closed by peer and a negative value when no more data could be read from the connection.
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### Example
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```
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#define RECV_BUF_SIZE 1 << 20
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size_t read_data(struct mg_connection* conn,
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uint8_t* buff,
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size_t buff_len) {
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size_t read_len = 0;
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while (read_len < buff_len) {
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size_t sz_to_read = std::min<size_t>(RECV_BUF_SIZE, buff_len - read_len);
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int this_read = mg_read(conn, buff + read_len, sz_to_read);
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if (this_read < 0) {
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std::cerr << "[error] Failed to read data" << std::endl;
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break;
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} else {
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read_len += size_t(this_read);
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if (this_read > 0) {
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std::cout << "[debug] Received " << this_read << " more bytes" << std::endl;
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}
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}
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}
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return read_len;
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}
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```
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### See Also
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* [`mg_printf();`](mg_printf.md)
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* [`mg_write();`](mg_write.md)
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