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This little library implements rudimentary format-string support. It is useful for porting 3rd-party code that ought not depend on a full libc. Issue #2064
100 lines
2.0 KiB
C++
100 lines
2.0 KiB
C++
/*
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* \brief Facility to write format string into character buffer
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* \author Norman Feske
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* \date 2006-07-17
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*/
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/*
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* Copyright (C) 2006-2017 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__FORMAT__SNPRINTF_H_
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#define _INCLUDE__FORMAT__SNPRINTF_H_
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#include <format/console.h>
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namespace Format {
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class String_console;
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using size_t = __SIZE_TYPE__;
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/**
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* Print format string into character buffer
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*
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* \param dst destination buffer
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* \param dst_len size of 'dst' in bytes
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* \param format format string followed by the list of arguments
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*
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* \return number of characters written to destination buffer
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*/
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inline size_t snprintf(char *dst, size_t dst_size, const char *format, ...)
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__attribute__((format(printf, 3, 4)));
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}
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class Format::String_console : public Console
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{
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private:
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char *_dst;
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size_t _dst_len;
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size_t _w_offset { 0 };
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/*
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* Noncopyable
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*/
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String_console &operator = (String_console const &);
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String_console(String_console const &);
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public:
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/**
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* Constructor
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*
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* \param dst destination character buffer
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* \param dst_len size of 'dst'
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*/
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String_console(char *dst, size_t dst_len)
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: _dst(dst), _dst_len(dst_len)
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{ _dst[0] = 0; }
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/**
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* Return number of characters in destination buffer
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*/
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size_t len() { return _w_offset; }
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/***********************
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** Console interface **
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***********************/
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void _out_char(char c) override
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{
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/* ensure to leave space for null-termination */
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if (_w_offset + 2 > _dst_len)
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return;
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_dst[_w_offset++] = c;
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_dst[_w_offset] = 0;
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}
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};
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inline Format::size_t Format::snprintf(char *dst, size_t dst_len, const char *format, ...)
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{
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va_list list;
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va_start(list, format);
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String_console sc(dst, dst_len);
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sc.vprintf(format, list);
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va_end(list);
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return sc.len();
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}
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#endif /* _INCLUDE__FORMAT__SNPRINTF_H_ */
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