/*
 * Copyright 2021 Google LLC
 * SPDX-License-Identifier: MIT
 */

#include "vkr_cs.h"

#include "vrend_iov.h"

void
vkr_cs_encoder_set_stream(struct vkr_cs_encoder *enc,
                          const struct iovec *iov,
                          int iov_count,
                          size_t offset,
                          size_t size)
{
   enc->stream.iov = iov;
   enc->stream.iov_count = iov_count;
   enc->stream.offset = offset;
   enc->stream.size = size;
   /* clear cache */
   enc->stream.cached_index = 0;
   enc->stream.cached_offset = 0;

   vkr_cs_encoder_seek_stream(enc, 0);
}

static bool
vkr_cs_encoder_translate_stream_offset(struct vkr_cs_encoder *enc,
                                       size_t offset,
                                       int *iov_index,
                                       size_t *iov_offset)
{
   int idx = 0;

   /* use or clear cache */
   if (offset >= enc->stream.cached_offset) {
      offset -= enc->stream.cached_offset;
      idx = enc->stream.cached_index;
   } else {
      enc->stream.cached_index = 0;
      enc->stream.cached_offset = 0;
   }

   while (true) {
      if (idx >= enc->stream.iov_count)
         return false;

      const struct iovec *iov = &enc->stream.iov[idx];
      if (offset < iov->iov_len)
         break;

      idx++;
      offset -= iov->iov_len;

      /* update cache */
      enc->stream.cached_index++;
      enc->stream.cached_offset += iov->iov_len;
   }

   *iov_index = idx;
   *iov_offset = offset;

   return true;
}

static void
vkr_cs_encoder_update_end(struct vkr_cs_encoder *enc)
{
   const struct iovec *iov = &enc->stream.iov[enc->next_iov - 1];
   const size_t iov_offset = enc->cur - (uint8_t *)iov->iov_base;
   const size_t iov_remain = iov->iov_len - iov_offset;

   if (enc->remaining_size >= iov_remain) {
      enc->end = enc->cur + iov_remain;
      enc->remaining_size -= iov_remain;
   } else {
      enc->end = enc->cur + enc->remaining_size;
      enc->remaining_size = 0;
   }
}

void
vkr_cs_encoder_seek_stream(struct vkr_cs_encoder *enc, size_t pos)
{
   const size_t offset = enc->stream.offset + pos;
   int iov_index;
   size_t iov_offset;
   if (pos > enc->stream.size ||
       !vkr_cs_encoder_translate_stream_offset(enc, offset, &iov_index, &iov_offset)) {
      vkr_cs_encoder_set_fatal(enc);
      return;
   }

   enc->remaining_size = enc->stream.size - pos;
   enc->next_iov = iov_index + 1;

   const struct iovec *iov = &enc->stream.iov[iov_index];
   enc->cur = iov->iov_base;
   enc->cur += iov_offset;

   vkr_cs_encoder_update_end(enc);
}

static bool
vkr_cs_encoder_next_iov(struct vkr_cs_encoder *enc)
{
   if (enc->next_iov >= enc->stream.iov_count)
      return false;

   const struct iovec *iov = &enc->stream.iov[enc->next_iov++];
   enc->cur = iov->iov_base;
   vkr_cs_encoder_update_end(enc);

   return true;
}

static uint8_t *
vkr_cs_encoder_get_ptr(struct vkr_cs_encoder *enc, size_t size, size_t *ptr_size)
{
   while (true) {
      uint8_t *ptr = enc->cur;
      const size_t avail = enc->end - enc->cur;

      if (avail) {
         *ptr_size = MIN2(size, avail);
         enc->cur += *ptr_size;
         return ptr;
      }

      if (!vkr_cs_encoder_next_iov(enc)) {
         *ptr_size = 0;
         return size ? NULL : ptr;
      }
   }
}

void
vkr_cs_encoder_write_internal(struct vkr_cs_encoder *enc,
                              size_t size,
                              const void *val,
                              size_t val_size)
{
   size_t pad_size = size - val_size;

   do {
      size_t ptr_size;
      uint8_t *ptr = vkr_cs_encoder_get_ptr(enc, val_size, &ptr_size);
      if (unlikely(!ptr)) {
         vkr_cs_encoder_set_fatal(enc);
         return;
      }

      memcpy(ptr, val, ptr_size);
      val = (const uint8_t *)val + ptr_size;
      val_size -= ptr_size;
   } while (val_size);

   while (pad_size) {
      size_t ptr_size;
      const void *ptr = vkr_cs_encoder_get_ptr(enc, pad_size, &ptr_size);
      if (unlikely(!ptr)) {
         vkr_cs_encoder_set_fatal(enc);
         return;
      }
      pad_size -= ptr_size;
   }
}

void
vkr_cs_decoder_init(struct vkr_cs_decoder *dec,
                    const struct util_hash_table_u64 *object_table)
{
   memset(dec, 0, sizeof(*dec));
   dec->object_table = object_table;
}

void
vkr_cs_decoder_fini(struct vkr_cs_decoder *dec)
{
   struct vkr_cs_decoder_temp_pool *pool = &dec->temp_pool;
   for (uint32_t i = 0; i < pool->buffer_count; i++)
      free(pool->buffers[i]);
   if (pool->buffers)
      free(pool->buffers);
}

static void
vkr_cs_decoder_sanity_check(const struct vkr_cs_decoder *dec)
{
   const struct vkr_cs_decoder_temp_pool *pool = &dec->temp_pool;
   assert(pool->buffer_count <= pool->buffer_max);
   if (pool->buffer_count) {
      assert(pool->buffers[pool->buffer_count - 1] <= pool->reset_to);
      assert(pool->reset_to <= pool->cur);
      assert(pool->cur <= pool->end);
   }

   assert(dec->cur <= dec->end);
}

static void
vkr_cs_decoder_gc_temp_pool(struct vkr_cs_decoder *dec)
{
   struct vkr_cs_decoder_temp_pool *pool = &dec->temp_pool;
   if (!pool->buffer_count)
      return;

   /* free all but the last buffer */
   if (pool->buffer_count > 1) {
      for (uint32_t i = 0; i < pool->buffer_count - 1; i++)
         free(pool->buffers[i]);

      pool->buffers[0] = pool->buffers[pool->buffer_count - 1];
      pool->buffer_count = 1;
   }

   pool->reset_to = pool->buffers[0];
   pool->cur = pool->buffers[0];

   pool->total_size = pool->end - pool->cur;

   vkr_cs_decoder_sanity_check(dec);
}

/**
 * Reset a decoder for reuse.
 */
void
vkr_cs_decoder_reset(struct vkr_cs_decoder *dec)
{
   /* dec->fatal_error is sticky */

   vkr_cs_decoder_gc_temp_pool(dec);

   dec->saved_state_count = 0;
   dec->cur = NULL;
   dec->end = NULL;
}

bool
vkr_cs_decoder_push_state(struct vkr_cs_decoder *dec)
{
   struct vkr_cs_decoder_temp_pool *pool = &dec->temp_pool;
   struct vkr_cs_decoder_saved_state *saved;

   if (dec->saved_state_count >= ARRAY_SIZE(dec->saved_states))
      return false;

   saved = &dec->saved_states[dec->saved_state_count++];
   saved->cur = dec->cur;
   saved->end = dec->end;

   saved->pool_buffer_count = pool->buffer_count;
   saved->pool_reset_to = pool->reset_to;
   /* avoid temp data corruption */
   pool->reset_to = pool->cur;

   vkr_cs_decoder_sanity_check(dec);

   return true;
}

void
vkr_cs_decoder_pop_state(struct vkr_cs_decoder *dec)
{
   struct vkr_cs_decoder_temp_pool *pool = &dec->temp_pool;
   const struct vkr_cs_decoder_saved_state *saved;

   assert(dec->saved_state_count);
   saved = &dec->saved_states[--dec->saved_state_count];
   dec->cur = saved->cur;
   dec->end = saved->end;

   /* restore only if pool->reset_to points to the same buffer */
   if (pool->buffer_count == saved->pool_buffer_count)
      pool->reset_to = saved->pool_reset_to;

   vkr_cs_decoder_sanity_check(dec);
}

static uint32_t
next_array_size(uint32_t cur_size, uint32_t min_size)
{
   const uint32_t next_size = cur_size ? cur_size * 2 : min_size;
   return next_size > cur_size ? next_size : 0;
}

static size_t
next_buffer_size(size_t cur_size, size_t min_size, size_t need)
{
   size_t next_size = cur_size ? cur_size * 2 : min_size;
   while (next_size < need) {
      next_size *= 2;
      if (!next_size)
         return 0;
   }
   return next_size;
}

static bool
vkr_cs_decoder_grow_temp_pool(struct vkr_cs_decoder *dec)
{
   struct vkr_cs_decoder_temp_pool *pool = &dec->temp_pool;
   const uint32_t buf_max = next_array_size(pool->buffer_max, 4);
   if (!buf_max)
      return false;

   uint8_t **bufs = realloc(pool->buffers, sizeof(*pool->buffers) * buf_max);
   if (!bufs)
      return false;

   pool->buffers = bufs;
   pool->buffer_max = buf_max;

   return true;
}

bool
vkr_cs_decoder_alloc_temp_internal(struct vkr_cs_decoder *dec, size_t size)
{
   struct vkr_cs_decoder_temp_pool *pool = &dec->temp_pool;

   if (pool->buffer_count >= pool->buffer_max) {
      if (!vkr_cs_decoder_grow_temp_pool(dec))
         return false;
      assert(pool->buffer_count < pool->buffer_max);
   }

   const size_t cur_buf_size =
      pool->buffer_count ? pool->end - pool->buffers[pool->buffer_count - 1] : 0;
   const size_t buf_size = next_buffer_size(cur_buf_size, 4096, size);
   if (!buf_size)
      return false;

   if (buf_size > VKR_CS_DECODER_TEMP_POOL_MAX_SIZE - pool->total_size)
      return false;

   uint8_t *buf = malloc(buf_size);
   if (!buf)
      return false;

   pool->total_size += buf_size;
   pool->buffers[pool->buffer_count++] = buf;
   pool->reset_to = buf;
   pool->cur = buf;
   pool->end = buf + buf_size;

   vkr_cs_decoder_sanity_check(dec);

   return true;
}