/*
 * Copyright (C) 2009, 2010 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License (not later!)
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "kbuffer.h"

#define MISSING_EVENTS (1 << 31)
#define MISSING_STORED (1 << 30)

#define COMMIT_MASK ((1 << 27) - 1)

enum {
        KBUFFER_FL_HOST_BIG_ENDIAN      = (1<<0),
        KBUFFER_FL_BIG_ENDIAN           = (1<<1),
        KBUFFER_FL_LONG_8               = (1<<2),
        KBUFFER_FL_OLD_FORMAT           = (1<<3),
};

#define ENDIAN_MASK (KBUFFER_FL_HOST_BIG_ENDIAN | KBUFFER_FL_BIG_ENDIAN)

/** kbuffer
 * @timestamp           - timestamp of current event
 * @lost_events         - # of lost events between this subbuffer and previous
 * @flags               - special flags of the kbuffer
 * @subbuffer           - pointer to the sub-buffer page
 * @data                - pointer to the start of data on the sub-buffer page
 * @index               - index from @data to the @curr event data
 * @curr                - offset from @data to the start of current event
 *                         (includes metadata)
 * @next                - offset from @data to the start of next event
 * @size                - The size of data on @data
 * @start               - The offset from @subbuffer where @data lives
 *
 * @read_4              - Function to read 4 raw bytes (may swap)
 * @read_8              - Function to read 8 raw bytes (may swap)
 * @read_long           - Function to read a long word (4 or 8 bytes with needed swap)
 */
struct kbuffer {
        unsigned long long      timestamp;
        long long               lost_events;
        unsigned long           flags;
        void                    *subbuffer;
        void                    *data;
        unsigned int            index;
        unsigned int            curr;
        unsigned int            next;
        unsigned int            size;
        unsigned int            start;

        unsigned int (*read_4)(void *ptr);
        unsigned long long (*read_8)(void *ptr);
        unsigned long long (*read_long)(struct kbuffer *kbuf, void *ptr);
        int (*next_event)(struct kbuffer *kbuf);
};

static void *zmalloc(size_t size)
{
        return calloc(1, size);
}

static int host_is_bigendian(void)
{
        unsigned char str[] = { 0x1, 0x2, 0x3, 0x4 };
        unsigned int *ptr;

        ptr = (unsigned int *)str;
        return *ptr == 0x01020304;
}

static int do_swap(struct kbuffer *kbuf)
{
        return ((kbuf->flags & KBUFFER_FL_HOST_BIG_ENDIAN) + kbuf->flags) &
                ENDIAN_MASK;
}

static unsigned long long __read_8(void *ptr)
{
        unsigned long long data = *(unsigned long long *)ptr;

        return data;
}

static unsigned long long __read_8_sw(void *ptr)
{
        unsigned long long data = *(unsigned long long *)ptr;
        unsigned long long swap;

        swap = ((data & 0xffULL) << 56) |
                ((data & (0xffULL << 8)) << 40) |
                ((data & (0xffULL << 16)) << 24) |
                ((data & (0xffULL << 24)) << 8) |
                ((data & (0xffULL << 32)) >> 8) |
                ((data & (0xffULL << 40)) >> 24) |
                ((data & (0xffULL << 48)) >> 40) |
                ((data & (0xffULL << 56)) >> 56);

        return swap;
}

static unsigned int __read_4(void *ptr)
{
        unsigned int data = *(unsigned int *)ptr;

        return data;
}

static unsigned int __read_4_sw(void *ptr)
{
        unsigned int data = *(unsigned int *)ptr;
        unsigned int swap;

        swap = ((data & 0xffULL) << 24) |
                ((data & (0xffULL << 8)) << 8) |
                ((data & (0xffULL << 16)) >> 8) |
                ((data & (0xffULL << 24)) >> 24);

        return swap;
}

static unsigned long long read_8(struct kbuffer *kbuf, void *ptr)
{
        return kbuf->read_8(ptr);
}

static unsigned int read_4(struct kbuffer *kbuf, void *ptr)
{
        return kbuf->read_4(ptr);
}

static unsigned long long __read_long_8(struct kbuffer *kbuf, void *ptr)
{
        return kbuf->read_8(ptr);
}

static unsigned long long __read_long_4(struct kbuffer *kbuf, void *ptr)
{
        return kbuf->read_4(ptr);
}

static unsigned long long read_long(struct kbuffer *kbuf, void *ptr)
{
        return kbuf->read_long(kbuf, ptr);
}

static int calc_index(struct kbuffer *kbuf, void *ptr)
{
        return (unsigned long)ptr - (unsigned long)kbuf->data;
}

static int __next_event(struct kbuffer *kbuf);

/**
 * kbuffer_alloc - allocat a new kbuffer
 * @size;       enum to denote size of word
 * @endian:     enum to denote endianness
 *
 * Allocates and returns a new kbuffer.
 */
struct kbuffer *
kbuffer_alloc(enum kbuffer_long_size size, enum kbuffer_endian endian)
{
        struct kbuffer *kbuf;
        int flags = 0;

        switch (size) {
        case KBUFFER_LSIZE_4:
                break;
        case KBUFFER_LSIZE_8:
                flags |= KBUFFER_FL_LONG_8;
                break;
        default:
                return NULL;
        }

        switch (endian) {
        case KBUFFER_ENDIAN_LITTLE:
                break;
        case KBUFFER_ENDIAN_BIG:
                flags |= KBUFFER_FL_BIG_ENDIAN;
                break;
        default:
                return NULL;
        }

        kbuf = zmalloc(sizeof(*kbuf));
        if (!kbuf)
                return NULL;

        kbuf->flags = flags;

        if (host_is_bigendian())
                kbuf->flags |= KBUFFER_FL_HOST_BIG_ENDIAN;

        if (do_swap(kbuf)) {
                kbuf->read_8 = __read_8_sw;
                kbuf->read_4 = __read_4_sw;
        } else {
                kbuf->read_8 = __read_8;
                kbuf->read_4 = __read_4;
        }

        if (kbuf->flags & KBUFFER_FL_LONG_8)
                kbuf->read_long = __read_long_8;
        else
                kbuf->read_long = __read_long_4;

        /* May be changed by kbuffer_set_old_format() */
        kbuf->next_event = __next_event;

        return kbuf;
}

/** kbuffer_free - free an allocated kbuffer
 * @kbuf:       The kbuffer to free
 *
 * Can take NULL as a parameter.
 */
void kbuffer_free(struct kbuffer *kbuf)
{
        free(kbuf);
}

static unsigned int type4host(struct kbuffer *kbuf,
                              unsigned int type_len_ts)
{
        if (kbuf->flags & KBUFFER_FL_BIG_ENDIAN)
                return (type_len_ts >> 29) & 3;
        else
                return type_len_ts & 3;
}

static unsigned int len4host(struct kbuffer *kbuf,
                             unsigned int type_len_ts)
{
        if (kbuf->flags & KBUFFER_FL_BIG_ENDIAN)
                return (type_len_ts >> 27) & 7;
        else
                return (type_len_ts >> 2) & 7;
}

static unsigned int type_len4host(struct kbuffer *kbuf,
                                  unsigned int type_len_ts)
{
        if (kbuf->flags & KBUFFER_FL_BIG_ENDIAN)
                return (type_len_ts >> 27) & ((1 << 5) - 1);
        else
                return type_len_ts & ((1 << 5) - 1);
}

static unsigned int ts4host(struct kbuffer *kbuf,
                            unsigned int type_len_ts)
{
        if (kbuf->flags & KBUFFER_FL_BIG_ENDIAN)
                return type_len_ts & ((1 << 27) - 1);
        else
                return type_len_ts >> 5;
}

/*
 * Linux 2.6.30 and earlier (not much ealier) had a different
 * ring buffer format. It should be obsolete, but we handle it anyway.
 */
enum old_ring_buffer_type {
        OLD_RINGBUF_TYPE_PADDING,
        OLD_RINGBUF_TYPE_TIME_EXTEND,
        OLD_RINGBUF_TYPE_TIME_STAMP,
        OLD_RINGBUF_TYPE_DATA,
};

static unsigned int old_update_pointers(struct kbuffer *kbuf)
{
        unsigned long long extend;
        unsigned int type_len_ts;
        unsigned int type;
        unsigned int len;
        unsigned int delta;
        unsigned int length;
        void *ptr = kbuf->data + kbuf->curr;

        type_len_ts = read_4(kbuf, ptr);
        ptr += 4;

        type = type4host(kbuf, type_len_ts);
        len = len4host(kbuf, type_len_ts);
        delta = ts4host(kbuf, type_len_ts);

        switch (type) {
        case OLD_RINGBUF_TYPE_PADDING:
                kbuf->next = kbuf->size;
                return 0;

        case OLD_RINGBUF_TYPE_TIME_EXTEND:
                extend = read_4(kbuf, ptr);
                extend <<= TS_SHIFT;
                extend += delta;
                delta = extend;
                ptr += 4;
                break;

        case OLD_RINGBUF_TYPE_TIME_STAMP:
                /* should never happen! */
                kbuf->curr = kbuf->size;
                kbuf->next = kbuf->size;
                kbuf->index = kbuf->size;
                return -1;
        default:
                if (len)
                        length = len * 4;
                else {
                        length = read_4(kbuf, ptr);
                        length -= 4;
                        ptr += 4;
                }
                break;
        }

        kbuf->timestamp += delta;
        kbuf->index = calc_index(kbuf, ptr);
        kbuf->next = kbuf->index + length;

        return type;
}

static int __old_next_event(struct kbuffer *kbuf)
{
        int type;

        do {
                kbuf->curr = kbuf->next;
                if (kbuf->next >= kbuf->size)
                        return -1;
                type = old_update_pointers(kbuf);
        } while (type == OLD_RINGBUF_TYPE_TIME_EXTEND || type == OLD_RINGBUF_TYPE_PADDING);

        return 0;
}

static unsigned int
translate_data(struct kbuffer *kbuf, void *data, void **rptr,
               unsigned long long *delta, int *length)
{
        unsigned long long extend;
        unsigned int type_len_ts;
        unsigned int type_len;

        type_len_ts = read_4(kbuf, data);
        data += 4;

        type_len = type_len4host(kbuf, type_len_ts);
        *delta = ts4host(kbuf, type_len_ts);

        switch (type_len) {
        case KBUFFER_TYPE_PADDING:
                *length = read_4(kbuf, data);
                break;

        case KBUFFER_TYPE_TIME_EXTEND:
                extend = read_4(kbuf, data);
                data += 4;
                extend <<= TS_SHIFT;
                extend += *delta;
                *delta = extend;
                *length = 0;
                break;

        case KBUFFER_TYPE_TIME_STAMP:
                data += 12;
                *length = 0;
                break;
        case 0:
                *length = read_4(kbuf, data) - 4;
                *length = (*length + 3) & ~3;
                data += 4;
                break;
        default:
                *length = type_len * 4;
                break;
        }

        *rptr = data;

        return type_len;
}

static unsigned int update_pointers(struct kbuffer *kbuf)
{
        unsigned long long delta;
        unsigned int type_len;
        int length;
        void *ptr = kbuf->data + kbuf->curr;

        type_len = translate_data(kbuf, ptr, &ptr, &delta, &length);

        kbuf->timestamp += delta;
        kbuf->index = calc_index(kbuf, ptr);
        kbuf->next = kbuf->index + length;

        return type_len;
}

/**
 * kbuffer_translate_data - read raw data to get a record
 * @swap:       Set to 1 if bytes in words need to be swapped when read
 * @data:       The raw data to read
 * @size:       Address to store the size of the event data.
 *
 * Returns a pointer to the event data. To determine the entire
 * record size (record metadata + data) just add the difference between
 * @data and the returned value to @size.
 */
void *kbuffer_translate_data(int swap, void *data, unsigned int *size)
{
        unsigned long long delta;
        struct kbuffer kbuf;
        int type_len;
        int length;
        void *ptr;

        if (swap) {
                kbuf.read_8 = __read_8_sw;
                kbuf.read_4 = __read_4_sw;
                kbuf.flags = host_is_bigendian() ? 0 : KBUFFER_FL_BIG_ENDIAN;
        } else {
                kbuf.read_8 = __read_8;
                kbuf.read_4 = __read_4;
                kbuf.flags = host_is_bigendian() ? KBUFFER_FL_BIG_ENDIAN: 0;
        }

        type_len = translate_data(&kbuf, data, &ptr, &delta, &length);
        switch (type_len) {
        case KBUFFER_TYPE_PADDING:
        case KBUFFER_TYPE_TIME_EXTEND:
        case KBUFFER_TYPE_TIME_STAMP:
                return NULL;
        };

        *size = length;

        return ptr;
}

static int __next_event(struct kbuffer *kbuf)
{
        int type;

        do {
                kbuf->curr = kbuf->next;
                if (kbuf->next >= kbuf->size)
                        return -1;
                type = update_pointers(kbuf);
        } while (type == KBUFFER_TYPE_TIME_EXTEND || type == KBUFFER_TYPE_PADDING);

        return 0;
}

static int next_event(struct kbuffer *kbuf)
{
        return kbuf->next_event(kbuf);
}

/**
 * kbuffer_next_event - increment the current pointer
 * @kbuf:       The kbuffer to read
 * @ts:         Address to store the next record's timestamp (may be NULL to ignore)
 *
 * Increments the pointers into the subbuffer of the kbuffer to point to the
 * next event so that the next kbuffer_read_event() will return a
 * new event.
 *
 * Returns the data of the next event if a new event exists on the subbuffer,
 * NULL otherwise.
 */
void *kbuffer_next_event(struct kbuffer *kbuf, unsigned long long *ts)
{
        int ret;

        if (!kbuf || !kbuf->subbuffer)
                return NULL;

        ret = next_event(kbuf);
        if (ret < 0)
                return NULL;

        if (ts)
                *ts = kbuf->timestamp;

        return kbuf->data + kbuf->index;
}

/**
 * kbuffer_load_subbuffer - load a new subbuffer into the kbuffer
 * @kbuf:       The kbuffer to load
 * @subbuffer:  The subbuffer to load into @kbuf.
 *
 * Load a new subbuffer (page) into @kbuf. This will reset all
 * the pointers and update the @kbuf timestamp. The next read will
 * return the first event on @subbuffer.
 *
 * Returns 0 on succes, -1 otherwise.
 */
int kbuffer_load_subbuffer(struct kbuffer *kbuf, void *subbuffer)
{
        unsigned long long flags;
        void *ptr = subbuffer;

        if (!kbuf || !subbuffer)
                return -1;

        kbuf->subbuffer = subbuffer;

        kbuf->timestamp = read_8(kbuf, ptr);
        ptr += 8;

        kbuf->curr = 0;

        if (kbuf->flags & KBUFFER_FL_LONG_8)
                kbuf->start = 16;
        else
                kbuf->start = 12;

        kbuf->data = subbuffer + kbuf->start;

        flags = read_long(kbuf, ptr);
        kbuf->size = (unsigned int)flags & COMMIT_MASK;

        if (flags & MISSING_EVENTS) {
                if (flags & MISSING_STORED) {
                        ptr = kbuf->data + kbuf->size;
                        kbuf->lost_events = read_long(kbuf, ptr);
                } else
                        kbuf->lost_events = -1;
        } else
                kbuf->lost_events = 0;

        kbuf->index = 0;
        kbuf->next = 0;

        next_event(kbuf);

        return 0;
}

/**
 * kbuffer_read_event - read the next event in the kbuffer subbuffer
 * @kbuf:       The kbuffer to read from
 * @ts:         The address to store the timestamp of the event (may be NULL to ignore)
 *
 * Returns a pointer to the data part of the current event.
 * NULL if no event is left on the subbuffer.
 */
void *kbuffer_read_event(struct kbuffer *kbuf, unsigned long long *ts)
{
        if (!kbuf || !kbuf->subbuffer)
                return NULL;

        if (kbuf->curr >= kbuf->size)
                return NULL;

        if (ts)
                *ts = kbuf->timestamp;
        return kbuf->data + kbuf->index;
}

/**
 * kbuffer_timestamp - Return the timestamp of the current event
 * @kbuf:       The kbuffer to read from
 *
 * Returns the timestamp of the current (next) event.
 */
unsigned long long kbuffer_timestamp(struct kbuffer *kbuf)
{
        return kbuf->timestamp;
}

/**
 * kbuffer_read_at_offset - read the event that is at offset
 * @kbuf:       The kbuffer to read from
 * @offset:     The offset into the subbuffer
 * @ts:         The address to store the timestamp of the event (may be NULL to ignore)
 *
 * The @offset must be an index from the @kbuf subbuffer beginning.
 * If @offset is bigger than the stored subbuffer, NULL will be returned.
 *
 * Returns the data of the record that is at @offset. Note, @offset does
 * not need to be the start of the record, the offset just needs to be
 * in the record (or beginning of it).
 *
 * Note, the kbuf timestamp and pointers are updated to the
 * returned record. That is, kbuffer_read_event() will return the same
 * data and timestamp, and kbuffer_next_event() will increment from
 * this record.
 */
void *kbuffer_read_at_offset(struct kbuffer *kbuf, int offset,
                             unsigned long long *ts)
{
        void *data;

        if (offset < kbuf->start)
                offset = 0;
        else
                offset -= kbuf->start;

        /* Reset the buffer */
        kbuffer_load_subbuffer(kbuf, kbuf->subbuffer);

        while (kbuf->curr < offset) {
                data = kbuffer_next_event(kbuf, ts);
                if (!data)
                        break;
        }

        return data;
}

/**
 * kbuffer_subbuffer_size - the size of the loaded subbuffer
 * @kbuf:       The kbuffer to read from
 *
 * Returns the size of the subbuffer. Note, this size is
 * where the last event resides. The stored subbuffer may actually be
 * bigger due to padding and such.
 */
int kbuffer_subbuffer_size(struct kbuffer *kbuf)
{
        return kbuf->size;
}

/**
 * kbuffer_curr_index - Return the index of the record
 * @kbuf:       The kbuffer to read from
 *
 * Returns the index from the start of the data part of
 * the subbuffer to the current location. Note this is not
 * from the start of the subbuffer. An index of zero will
 * point to the first record. Use kbuffer_curr_offset() for
 * the actually offset (that can be used by kbuffer_read_at_offset())
 */
int kbuffer_curr_index(struct kbuffer *kbuf)
{
        return kbuf->curr;
}

/**
 * kbuffer_curr_offset - Return the offset of the record
 * @kbuf:       The kbuffer to read from
 *
 * Returns the offset from the start of the subbuffer to the
 * current location.
 */
int kbuffer_curr_offset(struct kbuffer *kbuf)
{
        return kbuf->curr + kbuf->start;
}

/**
 * kbuffer_event_size - return the size of the event data
 * @kbuf:       The kbuffer to read
 *
 * Returns the size of the event data (the payload not counting
 * the meta data of the record) of the current event.
 */
int kbuffer_event_size(struct kbuffer *kbuf)
{
        return kbuf->next - kbuf->index;
}

/**
 * kbuffer_curr_size - return the size of the entire record
 * @kbuf:       The kbuffer to read
 *
 * Returns the size of the entire record (meta data and payload)
 * of the current event.
 */
int kbuffer_curr_size(struct kbuffer *kbuf)
{
        return kbuf->next - kbuf->curr;
}

/**
 * kbuffer_missed_events - return the # of missed events from last event.
 * @kbuf:       The kbuffer to read from
 *
 * Returns the # of missed events (if recorded) before the current
 * event. Note, only events on the beginning of a subbuffer can
 * have missed events, all other events within the buffer will be
 * zero.
 */
int kbuffer_missed_events(struct kbuffer *kbuf)
{
        /* Only the first event can have missed events */
        if (kbuf->curr)
                return 0;

        return kbuf->lost_events;
}

/**
 * kbuffer_set_old_forma - set the kbuffer to use the old format parsing
 * @kbuf:       The kbuffer to set
 *
 * This is obsolete (or should be). The first kernels to use the
 * new ring buffer had a slightly different ring buffer format
 * (2.6.30 and earlier). It is still somewhat supported by kbuffer,
 * but should not be counted on in the future.
 */
void kbuffer_set_old_format(struct kbuffer *kbuf)
{
        kbuf->flags |= KBUFFER_FL_OLD_FORMAT;

        kbuf->next_event = __old_next_event;
}

/**
 * kbuffer_start_of_data - return offset of where data starts on subbuffer
 * @kbuf:       The kbuffer
 *
 * Returns the location on the subbuffer where the data starts.
 */
int kbuffer_start_of_data(struct kbuffer *kbuf)
{
        return kbuf->start;
}