// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef DDK_PHYS_ITER_H_
#define DDK_PHYS_ITER_H_

#include <zircon/types.h>

__BEGIN_CDECLS

// An entry in a scatter gather list.
typedef struct {
    // length starting at the scatter gather entry offset, must be non zero
    size_t length;
    // offset relative to the buffer's vmo_offset
    size_t offset;
} phys_iter_sg_entry_t;

// Specifies the buffer to iterate over.
typedef struct {
    const zx_paddr_t* phys; // list of physical addresses backing the buffer starting at vmo_offset
    uint64_t phys_count;    // number of entries in phys list

    size_t length;       // length of the buffer starting at vmo_offset, used if scatter gather
                         // list is not present
    uint64_t vmo_offset; // offset into first page to start iterating on

    const phys_iter_sg_entry_t* sg_list; // optional list of scatter gather entries to iterate over
    size_t sg_count;               // number of entries in the scatter gather list
} phys_iter_buffer_t;

// Used to iterate over contiguous buffer ranges in the physical address space.
typedef struct {
    phys_iter_buffer_t buf;

    size_t total_iterated; // total bytes iterated across all calls for this iterator
    zx_off_t offset;       // current offset in the segment (relative to the segment offset)
                           // i.e. the total number of bytes iterated for the current segment
    size_t max_length;     // max length to be returned by phys_iter_next()
    uint64_t page;         // index of page in buf->phys that contains offset
    uint64_t last_page;    // last valid page index in buf->phys

    size_t next_sg_entry_idx; // next index in the scatter gather list
    size_t segment_offset;    // offset of the current scatter gather entry, relative to buffer
                              // vmo_offset, or zero if no scatter gather list is present.
    size_t segment_length;    // length of the buffer for the current scatter gather entry,
                              // or equal to buf.length if no scatter gather list is present.
} phys_iter_t;

// Initializes a phys_iter_t for iterating over physical memory.
// max_length is the maximum length of a range returned by phys_iter_next()
// max_length must be either a positive multiple of PAGE_SIZE, or zero for no limit.
void phys_iter_init(phys_iter_t* iter, const phys_iter_buffer_t* buf, size_t max_length);

// Returns the next physical address and length for the iterator up to size max_length.
// Return value is length, or zero if iteration is done.
size_t phys_iter_next(phys_iter_t* iter, zx_paddr_t* out_paddr);

__END_CDECLS

#ifdef __cplusplus

#include <utility>

namespace ddk {

// Wrapper around phys_iter_t that provides C++ iterator support.
class PhysIter {
private:
    class iterator_impl;

public:
    PhysIter(const phys_iter_buffer_t& buf, size_t max_length) {
        phys_iter_init(&iter_, &buf, max_length);
    }

    using PhysPair = std::pair<zx_paddr_t, size_t>;

    using const_iterator = iterator_impl;

    const_iterator begin() const { return const_iterator(iter_, false); }
    const_iterator cbegin() const { return const_iterator(iter_, false); }
    const_iterator end() const { return const_iterator(iter_, true); }
    const_iterator cend() const { return const_iterator(iter_, true); }

private:
    class iterator_impl {
    public:
        iterator_impl(const iterator_impl& other) = default;
        iterator_impl& operator=(const iterator_impl& other) = default;

        bool operator==(const iterator_impl& other) const { return current_ == other.current_; }
        bool operator!=(const iterator_impl& other) const { return current_ != other.current_; }

        const PhysPair& operator*() const { return current_; }

        // Prefix
        iterator_impl& operator++() {
            if (current_.second == 0) {
                return *this;
            }
            current_.second = phys_iter_next(&iter_, &current_.first);
            return *this;
        }

        // Postfix
        iterator_impl operator++(int) {
            iterator_impl ret(*this);
            ++(*this);
            return ret;
        }

    private:
        friend class PhysIter;

        iterator_impl(const phys_iter_t& iter, bool last)
            : iter_(iter) {

            current_.second = phys_iter_next(&iter_, &current_.first);
            while (last && current_.second != 0) {
                current_.second = phys_iter_next(&iter_, &current_.first);
            };
        }

        phys_iter_t iter_;
        PhysPair current_ = {};
    };

    phys_iter_t iter_;
};

} // namespace ddk
#endif

#endif  // DDK_PHYS_ITER_H_