enhance ledger-tool

* add json, which does the thing with json, move print to Rust's {:?}
  * add --head NUM, to limit how much work gets done for print, json, verify
  * add verify-internal, which very carefully checks ledger format without
      trying first to "recover" it
  * exit with errors on mis-usage

src/bin/ledger-tool.rs

@@ -5,7 +5,7 @@ extern crate solana;
 
 use clap::{App, Arg, SubCommand};
 use solana::bank::Bank;
-use solana::ledger::read_ledger;
+use solana::ledger::{read_ledger, verify_ledger};
 use solana::logger;
 use std::io::{stdout, Write};
 use std::process::exit;
@@ -23,23 +23,57 @@ fn main() {
                 .required(true)
                 .help("use DIR for ledger location"),
         )
+        .arg(
+            Arg::with_name("head")
+                .short("n")
+                .long("head")
+                .value_name("NUM")
+                .takes_value(true)
+                .help("at most the first NUM entries in ledger\n  (only applies to verify, print, json commands)"),
+        )
         .subcommand(SubCommand::with_name("print").about("Print the ledger"))
-        .subcommand(SubCommand::with_name("verify").about("Verify the ledger"))
+        .subcommand(SubCommand::with_name("json").about("Print the ledger in JSON format"))
+        .subcommand(SubCommand::with_name("verify").about("Verify the ledger's PoH"))
+        .subcommand(
+            SubCommand::with_name("verify-internal")
+                .about("Verify the ledger's internal structure"),
+        )
         .get_matches();
 
     let ledger_path = matches.value_of("ledger").unwrap();
     let entries = match read_ledger(ledger_path, true) {
         Ok(entries) => entries,
         Err(err) => {
-            println!("Failed to open ledger at {}: {}", ledger_path, err);
+            eprintln!("Failed to open ledger at {}: {}", ledger_path, err);
             exit(1);
         }
     };
 
+    let head = match matches.value_of("head") {
+        Some(head) => head.parse().expect("please pass a number for --head"),
+        None => <usize>::max_value(),
+    };
+
     match matches.subcommand() {
         ("print", _) => {
+            let mut i = 0;
+            for entry in entries {
+                if i >= head {
+                    break;
+                }
+                i += 1;
+                let entry = entry.unwrap();
+                println!("{:?}", entry);
+            }
+        }
+        ("json", _) => {
+            let mut i = 0;
             stdout().write_all(b"{\"ledger\":[\n").expect("open array");
             for entry in entries {
+                if i >= head {
+                    break;
+                }
+                i += 1;
                 let entry = entry.unwrap();
                 serde_json::to_writer(stdout(), &entry).expect("serialize");
                 stdout().write_all(b",\n").expect("newline");
@@ -47,13 +81,27 @@ fn main() {
             stdout().write_all(b"\n]}\n").expect("close array");
         }
         ("verify", _) => {
-            let entries = entries.map(|entry| entry.unwrap());
             let bank = Bank::default();
-            let entry_height = bank.process_ledger(entries).expect("process_ledger").0;
-            println!("Ledger is valid.  Height: {}", entry_height);
+            if head != <usize>::max_value() {
+                let entries = entries.map(|entry| entry.unwrap()).take(head);
+                bank.process_ledger(entries).expect("process_ledger").0;
+            } else {
+                let entries = entries.map(|entry| entry.unwrap());
+                bank.process_ledger(entries).expect("process_ledger").0;
             }
+        }
+        ("verify-internal", _) => {
+            if let Err(e) = verify_ledger(&ledger_path, false) {
+                eprintln!("Error {:?} ", e);
+                exit(1);
+            } else {
+                println!("Ledger is valid");
+            }
+        }
+
         ("", _) => {
-            println!("{}", matches.usage());
+            eprintln!("{}", matches.usage());
+            exit(1);
         }
         _ => unreachable!(),
     };