util/stream/stream_string.c

Go to the documentation of this file.

#include <util.h>
#include <string.h>
#include <stream.h>
#include <compiler.h>

#define BUFFER_STREAM_BUFFER_SIZE       32

struct string_stream {
        struct stream   stream;
        size_t          offset;
        size_t          size;
        char            *string;
        char            buffer[BUFFER_STREAM_BUFFER_SIZE];
};

static inline struct string_stream *string_stream_of(struct stream *s)
{
        return container_of(s, struct string_stream, stream);
}

static void snprintf_stream_commit(struct stream *s)
{
        struct string_stream    *ss = string_stream_of(s);

        /* Make sure no data outside the output string buffer is written. */

        while (stream_buf_has_data(s) && ss->offset < ss->size) {
                ss->string[ss->offset] = stream_buf_extract_char(s);
                /*
                 * Move data offset in buffer to point to next available byte.
                 */
                ss->offset++;
        }

        /* Compensate offset for trailing null byte, i.e., add 1. */
        if (stream_buf_has_data(s) && (ss->offset + 1) >= ss->size) {
                /*
                 * If there still is data in the stream, do dummy read to free
                 * up the private buffer. Basically toss away the remaining
                 * characters.
                 */
                while (stream_buf_has_data(s)) {
                        stream_buf_extract_char(s);
                }
        }
}

static void sprintf_stream_commit(struct stream *s)
{
        struct string_stream    *ss = string_stream_of(s);

        while (stream_buf_has_data(s)) {
                ss->string[ss->offset] = stream_buf_extract_char(s);
                /*
                 * Move data offset in buffer to point to next available byte.
                 */
                ss->offset++;
        }
}

static bool string_stream_make_room(struct stream *s, unsigned int goal)
{
        s->ops->commit(s);
        return true;
}

static const struct stream_ops snprintf_stream_ops = {
        .commit         = snprintf_stream_commit,
        .make_room      = string_stream_make_room,
};

static const struct stream_ops sprintf_stream_ops = {
        .commit         = sprintf_stream_commit,
        .make_room      = string_stream_make_room,
};

int snprintf(char *str, size_t size, const char *format, ...)
{
        int n;
        va_list ap;
        struct string_stream ss = {
                {
                        .ops            = &snprintf_stream_ops,
                        .ring_mask      = BUFFER_STREAM_BUFFER_SIZE - 1,
                },
                .string = str,
                .offset = 0,
                /*
                 * Subtract one from the size to have room for the trailing
                 * null byte.
                 */
                .size   = size - 1,
        };

        va_start(ap, format);

        memset(ss.buffer, 0, BUFFER_STREAM_BUFFER_SIZE);
        ss.stream.data = ss.buffer;
        n = stream_vprintf(&ss.stream, format, ap);

        va_end(ap);

        /* Add null character termination to stream. */
        if (ss.offset >= size)
                str[ss.offset - 1] = '\0';
        else
                str[ss.offset] = '\0';

        return n;
}

int sprintf(char *str, const char *format, ...)
{
        int n;
        va_list ap;
        struct string_stream ss = {
                {
                        .ops            = &sprintf_stream_ops,
                        .ring_mask      = BUFFER_STREAM_BUFFER_SIZE - 1,
                },
                .string = str,
                .offset = 0,
        };

        va_start(ap, format);

        memset(ss.buffer, 0, BUFFER_STREAM_BUFFER_SIZE);
        ss.stream.data = ss.buffer;
        n = stream_vprintf(&ss.stream, format, ap);

        va_end(ap);

        /* Add null character termination to stream. */
        str[ss.offset] = '\0';

        return n;
}

---