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101 lines
2.6 KiB
C++
101 lines
2.6 KiB
C++
/*
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* \brief Utility for safely writing multi-line text
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* \author Norman Feske
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* \date 2014-01-11
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*/
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/*
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* Copyright (C) 2014-2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__UTIL__PRINT_LINES_H_
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#define _INCLUDE__UTIL__PRINT_LINES_H_
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#include <util/string.h>
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namespace Genode {
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template <size_t>
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static inline void print_lines(char const *, size_t, auto const &);
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}
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/**
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* Print multi-line string
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*
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* \param MAX_LINE_LEN maximum line length, used to dimension a line buffer
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* on the stack
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* \param string character buffer, not necessarily null-terminated
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* \param len number of characters to print
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* \param fn functor called for each line with 'char const *' as
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* argument
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*
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* In situations where a string is supplied by an untrusted client, we cannot
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* simply print the client-provided content as a single string becausewe cannot
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* expect the client to null-terminate the string properly. The 'Log_multiline'
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* class outputs the content line by line while keeping track of the content
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* size.
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*
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* The output stops when reaching the end of the buffer or when a null
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* character is encountered.
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*/
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template <Genode::size_t MAX_LINE_LEN>
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void Genode::print_lines(char const *string, size_t len, auto const &fn)
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{
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/* skip leading line breaks */
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for (; *string == '\n'; string++);
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/* number of space and tab characters used for indentation */
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size_t const num_indent_chars =
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({
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size_t n = 0;
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for (; string[n] == ' ' || string[n] == '\t'; n++);
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n;
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});
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char const * const first_line = string;
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while (*string && len) {
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/*
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* Skip indentation if the pattern is the same as for the first line.
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*/
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if (Genode::strcmp(first_line, string, num_indent_chars) == 0)
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string += num_indent_chars;
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size_t line_len = 0;
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size_t skip_char = 0;
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for (; line_len < len; line_len++) {
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if (string[line_len] == '\0' || string[line_len] == '\n') {
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line_len++;
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skip_char = 1;
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break;
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}
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if (line_len == MAX_LINE_LEN)
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break;
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}
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if (!line_len)
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break;
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/* buffer for sub-string of the input string plus null-termination */
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char line_buf[MAX_LINE_LEN + 1];
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/* one more byte for the null termination */
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copy_cstring(line_buf, string, line_len - skip_char + 1);
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/* process null-terminated string in buffer */
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fn(line_buf);
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/* move forward to the next sub-string to process */
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string += line_len;
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len -= line_len;
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}
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}
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#endif /* _INCLUDE__UTIL__PRINT_LINES_H_ */
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