// SPDX-License-Identifier: GPL-2.0
/*
 * C++ stream style string builder used in KUnit for building messages.
 *
 * Copyright (C) 2019, Google LLC.
 * Author: Brendan Higgins <brendanhiggins@google.com>
 */

#include <kunit/static_stub.h>
#include <kunit/test.h>
#include <linux/list.h>
#include <linux/slab.h>

#include "string-stream.h"


static struct string_stream_fragment *alloc_string_stream_fragment(int len, gfp_t gfp)
{
        struct string_stream_fragment *frag;

        frag = kzalloc_obj(*frag, gfp);
        if (!frag)
                return ERR_PTR(-ENOMEM);

        frag->fragment = kmalloc(len, gfp);
        if (!frag->fragment) {
                kfree(frag);
                return ERR_PTR(-ENOMEM);
        }

        return frag;
}

static void string_stream_fragment_destroy(struct string_stream_fragment *frag)
{
        list_del(&frag->node);
        kfree(frag->fragment);
        kfree(frag);
}

int string_stream_vadd(struct string_stream *stream,
                       const char *fmt,
                       va_list args)
{
        struct string_stream_fragment *frag_container;
        int buf_len, result_len;
        va_list args_for_counting;

        /* Make a copy because `vsnprintf` could change it */
        va_copy(args_for_counting, args);

        /* Evaluate length of formatted string */
        buf_len = vsnprintf(NULL, 0, fmt, args_for_counting);

        va_end(args_for_counting);

        if (buf_len == 0)
                return 0;

        /* Reserve one extra for possible appended newline. */
        if (stream->append_newlines)
                buf_len++;

        /* Need space for null byte. */
        buf_len++;

        frag_container = alloc_string_stream_fragment(buf_len, stream->gfp);
        if (IS_ERR(frag_container))
                return PTR_ERR(frag_container);

        if (stream->append_newlines) {
                /* Don't include reserved newline byte in writeable length. */
                result_len = vsnprintf(frag_container->fragment, buf_len - 1, fmt, args);

                /* Append newline if necessary. */
                if (frag_container->fragment[result_len - 1] != '\n')
                        result_len = strlcat(frag_container->fragment, "\n", buf_len);
        } else {
                result_len = vsnprintf(frag_container->fragment, buf_len, fmt, args);
        }

        spin_lock(&stream->lock);
        stream->length += result_len;
        list_add_tail(&frag_container->node, &stream->fragments);
        spin_unlock(&stream->lock);

        return 0;
}

int string_stream_add(struct string_stream *stream, const char *fmt, ...)
{
        va_list args;
        int result;

        va_start(args, fmt);
        result = string_stream_vadd(stream, fmt, args);
        va_end(args);

        return result;
}

void string_stream_clear(struct string_stream *stream)
{
        struct string_stream_fragment *frag_container, *frag_container_safe;

        spin_lock(&stream->lock);
        list_for_each_entry_safe(frag_container,
                                 frag_container_safe,
                                 &stream->fragments,
                                 node) {
                string_stream_fragment_destroy(frag_container);
        }
        stream->length = 0;
        spin_unlock(&stream->lock);
}

char *string_stream_get_string(struct string_stream *stream)
{
        struct string_stream_fragment *frag_container;
        size_t buf_len = stream->length + 1; /* +1 for null byte. */
        char *buf;

        buf = kzalloc(buf_len, stream->gfp);
        if (!buf)
                return NULL;

        spin_lock(&stream->lock);
        list_for_each_entry(frag_container, &stream->fragments, node)
                strlcat(buf, frag_container->fragment, buf_len);
        spin_unlock(&stream->lock);

        return buf;
}

int string_stream_append(struct string_stream *stream,
                         struct string_stream *other)
{
        const char *other_content;
        int ret;

        other_content = string_stream_get_string(other);

        if (!other_content)
                return -ENOMEM;

        ret = string_stream_add(stream, other_content);
        kfree(other_content);

        return ret;
}

bool string_stream_is_empty(struct string_stream *stream)
{
        return list_empty(&stream->fragments);
}

struct string_stream *alloc_string_stream(gfp_t gfp)
{
        struct string_stream *stream;

        stream = kzalloc_obj(*stream, gfp);
        if (!stream)
                return ERR_PTR(-ENOMEM);

        stream->gfp = gfp;
        INIT_LIST_HEAD(&stream->fragments);
        spin_lock_init(&stream->lock);

        return stream;
}

void string_stream_destroy(struct string_stream *stream)
{
        KUNIT_STATIC_STUB_REDIRECT(string_stream_destroy, stream);

        if (IS_ERR_OR_NULL(stream))
                return;

        string_stream_clear(stream);
        kfree(stream);
}

static void resource_free_string_stream(void *p)
{
        struct string_stream *stream = p;

        string_stream_destroy(stream);
}

struct string_stream *kunit_alloc_string_stream(struct kunit *test, gfp_t gfp)
{
        struct string_stream *stream;

        stream = alloc_string_stream(gfp);
        if (IS_ERR(stream))
                return stream;

        if (kunit_add_action_or_reset(test, resource_free_string_stream, stream) != 0)
                return ERR_PTR(-ENOMEM);

        return stream;
}

void kunit_free_string_stream(struct kunit *test, struct string_stream *stream)
{
        kunit_release_action(test, resource_free_string_stream, (void *)stream);
}