From 38438778f0fc34df8cdf748cc9f35e1d15e0c8db Mon Sep 17 00:00:00 2001 From: Evan Cox Date: Thu, 19 Oct 2017 11:40:10 -0500 Subject: [PATCH] Fix bus_t bug with devices at 0x0 Fix a bug that prevented bus_t from storing to, loading from, or finding a device that existed at address 0x0. Resolves: #135 --- riscv/devices.cc | 40 ++++++++++++++++++++++++++++++---------- 1 file changed, 30 insertions(+), 10 deletions(-) diff --git a/riscv/devices.cc b/riscv/devices.cc index 15115c8..bcdd3a1 100644 --- a/riscv/devices.cc +++ b/riscv/devices.cc @@ -2,29 +2,49 @@ void bus_t::add_device(reg_t addr, abstract_device_t* dev) { - devices[-addr] = dev; + // Searching devices via lower_bound/upper_bound + // implicitly relies on the underlying std::map + // container to sort the keys and provide ordered + // iteration over this sort, which it does. (python's + // SortedDict is a good analogy) + devices[addr] = dev; } bool bus_t::load(reg_t addr, size_t len, uint8_t* bytes) { - auto it = devices.lower_bound(-addr); - if (it == devices.end()) + // Find the device with the base address closest to but + // less than addr (price-is-right search) + auto it = devices.upper_bound(addr); + if (devices.empty() || it == devices.begin()) { + // Either the bus is empty, or there weren't + // any items with a base address <= addr return false; - return it->second->load(addr - -it->first, len, bytes); + } + // Found at least one item with base address <= addr + // The iterator points to the device after this, so + // go back by one item. + it--; + return it->second->load(addr - it->first, len, bytes); } bool bus_t::store(reg_t addr, size_t len, const uint8_t* bytes) { - auto it = devices.lower_bound(-addr); - if (it == devices.end()) + // See comments in bus_t::load + auto it = devices.upper_bound(addr); + if (devices.empty() || it == devices.begin()) { return false; - return it->second->store(addr - -it->first, len, bytes); + } + it--; + return it->second->store(addr - it->first, len, bytes); } std::pair bus_t::find_device(reg_t addr) { - auto it = devices.lower_bound(-addr); - if (it == devices.end() || addr < -it->first) + // See comments in bus_t::load + auto it = devices.upper_bound(addr); + if (devices.empty() || it == devices.begin()) { return std::make_pair((reg_t)0, (abstract_device_t*)NULL); - return std::make_pair(-it->first, it->second); + } + it--; + return std::make_pair(it->first, it->second); } -- 2.30.2