diff options
Diffstat (limited to 'lib/libc/README.txt')
-rw-r--r-- | lib/libc/README.txt | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/lib/libc/README.txt b/lib/libc/README.txt new file mode 100644 index 0000000..eaafdf4 --- /dev/null +++ b/lib/libc/README.txt @@ -0,0 +1,49 @@ + + Standard C library for the SLOF firmware project + ================================================ + +To use this library, link your target against the "libc.a" archive. + +However, there are some prerequisites before you can use certain parts of the +library: + +1) If you want to use malloc() and the like, you have to supply an implemen- + tation of sbrk() in your own code. malloc() uses sbrk() to get new, free + memory regions. + + Prototype: void *sbrk(int incr); + Description: sbrk() increments the available data space by incr bytes and + returns a pointer to the start of the new area. + + See the man-page of sbrk for details about this function. + +2) Before you can use the stdio output functions like printf(), puts() and the + like, you have to provide a standard write() function in your code. + printf() and the like use write() to print out the strings to the standard + output. + + Prototype: ssize_t write(int fd, const void *buf, size_t cnt); + Description: Write cnt byte from the buffer buf to the stream associated + with the file descriptor fd. + + The stdio functions will print their output to the stdout channel which is + assigned with the file descriptor 1 by default. Note that the stdio + functions will not use open() before calling write(), so if the stdout + cannel needs to be opened first, you should do that in your start-up code + before using the libc functions for the first time. + +3) Before you can use the stdio input functions like scanf() and the + like, you have to provide a standard read() function in your code. + scanf() and the like use read() to get the characters from the standard + input. + + Prototype: ssize_t read(int fd, void *buf, size_t cnt); + Description: Read cnt byte from the stream associated with the file + descriptor fd and put them into the buffer buf. + + The stdio functions will get their input from the stdin channel which is + assigned with the file descriptor 0 by default. Note that the stdio + functions will not use open() before calling read(), so if the stdin + cannel needs to be opened first, you should do that in your start-up code + before using the libc functions for the first time. + |