Add sysvar support (#5838)

programs/bpf/rust/clock/Cargo.toml

@@ -2,9 +2,9 @@
 # Note: This crate must be built using build.sh
 
 [package]
-name = "solana-bpf-rust-tick-height"
+name = "solana-bpf-rust-clock"
 version = "0.19.0-pre0"
-description = "Solana BPF noop program written in Rust"
+description = "Solana BPF clock sysvar test"
 authors = ["Solana Maintainers <maintainers@solana.com>"]
 repository = "https://github.com/solana-labs/solana"
 license = "Apache-2.0"
@@ -12,7 +12,6 @@ homepage = "https://solana.com/"
 edition = "2018"
 
 [dependencies]
-byteorder = { version = "1", default-features = false }
 solana-sdk = { path = "../../../../sdk/", version = "0.19.0-pre0", default-features = false }
 
 [features]
@@ -24,4 +23,4 @@ members = []
 
 [lib]
 crate-type = ["cdylib"]
-name = "solana_bpf_rust_tick_height"
+name = "solana_bpf_rust_clock"

programs/bpf/rust/clock/src/lib.rs

@@ -0,0 +1,28 @@
+//! @brief Example Rust-based BPF program that prints out the parameters passed to it
+
+extern crate solana_sdk;
+use solana_sdk::{
+    account_info::AccountInfo, entrypoint, entrypoint::SUCCESS, info, pubkey::Pubkey,
+    sysvar::clock::Clock,
+};
+
+entrypoint!(process_instruction);
+fn process_instruction(_program_id: &Pubkey, accounts: &mut [AccountInfo], _data: &[u8]) -> u32 {
+    match Clock::from(&accounts[2]) {
+        Some(clock) => {
+            info!("slot, segment, epoch, stakers_epoch");
+            info!(
+                clock.slot,
+                clock.segment, clock.epoch, clock.stakers_epoch, 0
+            );
+            assert_eq!(clock.slot, 42);
+        }
+        None => {
+            info!("Failed to get clock from account 2");
+            panic!();
+        }
+    }
+
+    info!("Success");
+    SUCCESS
+}

programs/bpf/rust/tick_height/src/lib.rs

@@ -1,16 +0,0 @@
-//! @brief Example Rust-based BPF program that prints out the parameters passed to it
-
-extern crate solana_sdk;
-use byteorder::{ByteOrder, LittleEndian};
-use solana_sdk::{
-    account_info::AccountInfo, entrypoint, entrypoint::SUCCESS, info, pubkey::Pubkey,
-};
-
-entrypoint!(process_instruction);
-fn process_instruction(_program_id: &Pubkey, accounts: &mut [AccountInfo], _data: &[u8]) -> u32 {
-    let tick_height = LittleEndian::read_u64(accounts[2].data);
-    assert_eq!(10u64, tick_height);
-
-    info!("Success");
-    SUCCESS
-}